1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Name of project which facilitated the documentation/ evaluation of the Technology (if relevant)

ICARDA Institutional Knowledge Management Initiative

Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)

International Center for Agricultural Research in the Dry Areas (ICARDA) - Lebanon

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:

Yes

1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?

No

2.1 Short description of the Technology

Definition of the Technology:

Conservation Agriculture (CA) is a "ready-to-scale concept" in agriculture that allows a sustainable agricultural production and mitigation of climate change. The documented CA focuses on a dryland mixed system, including a biennial rotation of legume and cereals with integrated livestock management. CA has positive benefits on soil health and significantly reduces the needed inputs (e.g. fuel, labour) and workload for farmers.

2.2 Detailed description of the Technology

Description:

Land degradation leading to desertification is an increasingly important problem in the dry land regions of the globe. This does not only affect the bio-physical aspects such as carbon storage, but also the lives of local land users. Land degradation is often initiated by the lack of vegetation cover as is often a consequence of overgrazing and over-ploughing (i.e mismanagement). Furthermore, climate change leads to droughts, intensified rainfall events, increased temperature, and more extreme weather events. These compromised climatic conditions enhance land degradation. This leads to less fertile soils, reducing yields and consequently deteriorates the income and lives of local farmers. Taking the consequence and scale of degradation into account, natural resource conservation interventions are urgently required.

As the lack of soil cover is an, if not the, essential initiating factor in the desertification process, it should be maximally addressed. In the light of this, CA has been developed, based on three leading principles: i) minimizing soil disturbances or no-tillage, ii) maintaining a permanent soil cover with mulch, and iii) adequate crop rotations. Overall, the three principles prevent land degradation and can also rehabilitate the land. This is because soil organic matter is maintained in/on the soil and the erosive power of raindrops are broken by the soil cover. Therefore, CA aims for more sustainable resource use (land and water use) and to optimize climate-resilient and integrated crop-livestock systems to sustainably intensify production in fragile dry areas.

Tunisia is a country that experiences the previously described pattern and results of desertification and where smallholder farmers are largely dependent on livestock for income generation. However, the livestock competes with the concept of CA as plant residues (stubble) are normally grazed by the livestock. Conservation agriculture propagates no or minimum soil disturbance/ tillage. However, the purchase of a zero-tillage seeder machine appears to be a bottleneck due to high costs since they are hardly produced locally. Nevertheless, there are farmers in the semi -arid areas of Tunisia, who adopted the technology and experience significant benefits such as increased soil fertility and over time increasing yields. In addition, as erosion rates are high in this rainfed area of 300 to 600 mm annual precipitation, a well-covered soil will reduce runoff and loss of top soil. Since ploughing is restricted, the workload and the demanded fuel is reduced, resulting in decreased costs and labour with respect to the conventional practices. Furthermore, integrated crop-livestock is practiced by limiting livestock to graze only the freshly harvested fields while producing manure to enhance soil health (organic fertilization and increase in soil organic matter).
Additionally, according to the third principle of CA, legumes were introduced in the agricultural system (crop rotation), besides the conventional cereal (e.g. durum wheat or barley). Specifically, faba bean is promising, as it has nitrogen fixing effects, enhancing soil health, and increasing and diversifying farm income. Vetch and other forage mixtures have also been successfully introduced to provide farmers with nutritious feed for livestock within the CA concept. In irrigated areas (e.g. parts in Algeria), the practice of CA has an additional benefit as it increases the irrigation water use efficiency due to less evaporation and better infiltration.

The previous agro-pastoral farming practices changed under CA to an integrated crop-livestock system where soil cover is permanent. This mixed system consist of firstly weed control. Secondly, zero-tillage seeding is done directly into the soil even if covered with e.g. mulch/stubble. Faba bean and/or wheat are seeded and rotated yearly. This is beneficial as legumes fix nitrogen in the soil, lowering the amount of nitrogenous fertilizer needed. Thirdly, required fertilizers (for wheat additional nitrogenous fertilizer) is applied with a spreader. Fourthly, herbicides, pesticides, insecticides and fungicides are applied with a sprayer for disease control. Fifthly, the field is harvested with a combine. The stubble is then partly grazed by the sheep and goats until there remains a 1-2 cm residue layer i.e. mulch. For one hectare this accounts for a thirty day grazing period for thirty goats or sheep. This results in an integrated Crop-Livestock system under CA (CLCA), as the stubble provides feed for livestock while the livestock provides the soil with manure.

The land users that have adopted CA have indicated that they extremely appreciate the reduction in work, also the cost of labour and fuel, etc. In addition, they saw increased yields due to improved soil health. However, this beneficial impact could only be observed in the long-term since yields take time to increase, which can be considered as a weakness as the small holder farmer tends to prioritize short term profits. Another weakness is that the livestock is constrained since residues ought to remain on the field.

In conclusion, even though there are bottlenecks, the technology of conservation agriculture is a solution to combat desertification while improving the lives of local land users through the process.

Information and data presented is partly made available through the project “Use of conservation agriculture in crop-livestock systems (CLCA) in the drylands for enhanced water use efficiency, soil fertility and productivity in NEN and LAC countries” funded by the International Fund for Agricultural Development (IFAD), managed by the International Center for Agricultural Research in the Dry Areas (ICARDA) and implemented in Tunisia by the National Agricultural Research Institute (INRAT).

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment

2.6 Date of implementation

Indicate year of implementation:

1999

2.7 Introduction of the Technology

Specify how the Technology was introduced:

• during experiments/ research
• through projects/ external interventions

3.1 Main purpose(s) of the Technology

• improve production
• reduce, prevent, restore land degradation
• adapt to climate change/ extremes and its impacts
• create beneficial economic impact

3.2 Current land use type(s) where the Technology is applied

Land use mixed within the same land unit:

Yes

Specify mixed land use (crops/ grazing/ trees):

• Agro-pastoralism (incl. integrated crop-livestock)

3.3 Has land use changed due to the implementation of the Technology?

Has land use changed due to the implementation of the Technology?

• Yes (Please fill out the questions below with regard to the land use before implementation of the Technology)

Land use mixed within the same land unit:

Yes

Specify mixed land use (crops/ grazing/ trees):

• Agro-pastoralism (incl. integrated crop-livestock)

Comments:

The land use has not necessarily changed as in the previous agro-pastoral system, livestock was also allowed to graze the field, providing it with manure. The difference is that under CA the livestock is not allowed to fully graze the land, leaving a soil cover.

3.4 Water supply

Water supply for the land on which the Technology is applied:

• rainfed

3.5 SLM group to which the Technology belongs

• integrated crop-livestock management
• improved ground/ vegetation cover
• minimal soil disturbance

3.6 SLM measures comprising the Technology

Comments:

The residues are partly retained and partly grazed.

3.7 Main types of land degradation addressed by the Technology

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:

• prevent land degradation
• restore/ rehabilitate severely degraded land

Comments:

The technology of CA prevents land degradation as the soil cover prevents erosion because the cover breaks the erosive power of rainfall and wind. Also, CA has the ability to rehabilitate as the content (like organic matter and carbon) of the soil cover (e.g. mulch/stubble) remains in the soil eventually improving the soil quality.

4.1 Technical drawing of the Technology

4.2 General information regarding the calculation of inputs and costs

Specify how costs and inputs were calculated:

• per Technology area

Specify currency used for cost calculations:

• USD

4.3 Establishment activities

	Activity	Timing (season)
1.	Purchase Zero-Tillage Seeder

4.4 Costs and inputs needed for establishment

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Equipment	Zero-Tillage Seeder	piece	1.0	20000.0	20000.0
Total costs for establishment of the Technology					20000.0
Total costs for establishment of the Technology in USD					20000.0

Comments:

The Zero-Tillage-Seeder can be bought as a community. This would lower the effective cost per farmer. Also, it is possible to hire Zero-Tillage Seeder.

4.5 Maintenance/ recurrent activities

	Activity	Timing/ frequency
1.	Weeding (Total weed control)	Year 1 Early-October
2.	Seeding Faba Bean	Year 1 Mid-October
3.	Apply Baseline Fertilization	Year 1 Mid-October
4.	Apply Herbicide	Year 1 Mid-October
5.	Apply Fungicide and Insecticide	Year 1 March-Early April
6.	Limited Grazing/Harvesting	Year 1 Late-April/May
7.	Weeding (Total weed control)	Year 2 Early-November
8.	Seeding Wheat	Year 2 Mid-November
9.	Apply Baseline Fertilization	Year 2 Mid-November
10.	Apply Nitrogenous Fertilization	Year 2 December-January-February
11.	Apply Herbicide	Year 2 December
12.	Apply Fungicide	Year 2 March-April
13.	Limited Grazing/Harvesting	Year 2 Late-June/Early-July

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

	Specify input	Unit	Quantity	Costs per Unit	Total costs per input	% of costs borne by land users
Labour	Weeding	Person-hour	1.0			100.0
Labour	Seeding	Person-hour	2.0			100.0
Labour	Fertilizer Application	Person-hour	0.5			100.0
Labour	Harvesting	Person-hour	2.0			100.0
Equipment	The Zero-Tillage Seeder (hiring cost)	Machine-hour	2.0	16.5	33.0	100.0
Equipment	Sprayer (hiring cost for disease control)	Machine-hour	4.5	11.0	49.5	100.0
Equipment	Spreader (hiring costs for nitrogenous fertilizer application)	Machine-hour	1.5	11.0	16.5	100.0
Equipment	Combine (hiring cost for harvesting)	Machine-hour	2.0	47.5	95.0	100.0
Plant material	Seeds Wheat	Kilogram	160.0	0.4	64.0	100.0
Plant material	Seeds Faba Bean	Kilogram	120.0	0.48	57.6	100.0
Fertilizers and biocides	Baseline Fertilization	Quintal	2.5	19.9	49.75	100.0
Fertilizers and biocides	Nitrogenous Fertilization	Quintal	3.0	15.5	46.5	100.0
Fertilizers and biocides	Pesticide (for total weed control)	Liter	2.0	10.0	20.0	100.0
Fertilizers and biocides	Herbicide for grassy weeds	Liter	1.0	41.2	41.2	100.0
Fertilizers and biocides	Herbicide for broadleaf weeds and sedges	Liter	2.0	29.2	58.4	100.0
Fertilizers and biocides	Fungicide	Liter	1.5	40.0	60.0	100.0
Fertilizers and biocides	Herbicide for annual and perennial grasses	Liter	1.25	25.5	31.88	100.0
Fertilizers and biocides	Insecticide	Liter	0.1	66.8	6.68	100.0
Other	Casual Labour	Person-day	12.0	5.3	63.6	100.0
Total costs for maintenance of the Technology					693.61
Total costs for maintenance of the Technology in USD					693.61

Comments:

Assuming a biennial rotation (Legume-Cereal), inputs and costs for the establishment of one hectare under the technology are displayed in the table. The costs for solely faba bean is 332.8 USD per hectare.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

The initial purchase of the zero-tillage machine (20 000 USD) is dominantly affecting the costs of the technology. However, it should be taken into account, that this machine serves the long term. Because the area under description is dominated by small-scale farmers, access to zero-tillage machines is ensured through hiring private entrepreneurs or through the purchase of machines by farmers’ associations rather than individual farmers. Also, it is important to note that the additional costs of conservation agriculture mainly consists of the machine, the weeding control and the seeding of the legumes. Other costs are either similar or reduced with respect to conventional agriculture. For example, conventional agriculture requires three hours of ploughing and 1 hour of sowing. While conservation agriculture only needs half an hour for chemical weeding, 1 hour for sowing and does not require ploughing. This relates to reduced inputs such as fuel.

5.1 Climate

5.2 Topography

Indicate if the Technology is specifically applied in:

• not relevant

5.3 Soils

If available, attach full soil description or specify the available information, e.g. soil type, soil PH/ acidity, Cation Exchange Capacity, nitrogen, salinity etc.

The top soil organic matter is relatively high as consequence of conservation agriculture.

5.4 Water availability and quality

Is water salinity a problem?

Yes

Is flooding of the area occurring?

No

5.5 Biodiversity

5.6 Characteristics of land users applying the Technology

5.7 Average area of land used by land users applying the Technology

5.8 Land ownership, land use rights, and water use rights

Land ownership:

• individual, not titled
• individual, titled

Land use rights:

• individual

Water use rights:

• communal (organized)
• individual

Are land use rights based on a traditional legal system?

Yes

Specify:

Land use rights in Tunisia have a long history with religious (e.g. melk) influences and French influences. This resulted in that currently most lands are private owned or state owned,

5.9 Access to services and infrastructure

6.1 On-site impacts the Technology has shown

Socio-economic impacts

Production

Income and costs

Socio-cultural impacts

Ecological impacts

Water cycle/ runoff

Soil

Biodiversity: vegetation, animals

Climate and disaster risk reduction

6.2 Off-site impacts the Technology has shown

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change

	Season	increase or decrease	How does the Technology cope with it?
annual temperature		increase	well
annual rainfall		decrease	well

Climate-related extremes (disasters)

Climatological disasters

	How does the Technology cope with it?
land fire	not well

Biological disasters

	How does the Technology cope with it?
epidemic diseases	not well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?

Comments:

The maintenance of conservation agriculture is positively experienced because of the reduced workload and inputs as the additional costs of e.g. weeding and pest control are not larger than the original costs of weeding and ploughing. However, the establishment costs are considered negative due to the significant costs of the zero-tillage machine. In the long term, the improved soil conditions should have maximum benefits.

6.5 Adoption of the Technology

• 1-10%

Of all those who have adopted the Technology, how many did so spontaneously, i.e. without receiving any material incentives/ payments?

• 11-50%

6.6 Adaptation

Has the Technology been modified recently to adapt to changing conditions?

Yes

other (specify):

The demand of the farmers

Specify adaptation of the Technology (design, material/ species, etc.):

The farmers demanded different dimensions for the Zero-Tillage-seeder, related to their desired inter rows spaces e.g. a wider seeder so more area is seeded in the same time.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Conservation Agriculture (CA) reduces the costs and workload with respects to conventional farming. For example, in conventional agriculture the field was ploughed, which costed machine hours. This cost is cancelled out by conservation agriculture, following the three principles. On top of that, this results in less costs such as depreciation of the plough and less consumed fuel.
CA leads to improved soil conditions and reduced/prevented land degradation which leads to increased biomass-production. This does benefit the land user. However, these benefits are noticeable in the long term. So, conservation agriculture is therefore significantly beneficial and (economically) important for family farms, where the land is passed on to future generations.
In irrigated areas, conservation agriculture leads to improved irrigation water use efficiency because of less water evaporation from the soil surface. Additionally, in flood irrigated areas, the soil is better protected and not flushed away. Farmers that have limited amount of irrigation water consider this a great benefit. In Algeria for example, the impact of CA practices resulted in a 30–40% reduction in the use of irrigation water and a two- to three-fold increase in barley and wheat production without the use of better seeds.

Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
In Tunisia, it has been proven that CA based on Zero tillage and soil residue retention vs conventional agriculture contributes to make wheat production more resilient to climate change through enhancing wheat yield (15%), improvement of water use efficiency (13% to 18%), increase organic carbon accumulation (0.13 ton/ha/year to 0.18 ton/ha/year-). The reduction of soil loss caused by soil water erosion varies between 1.7 ton/ha/year to 4.6 ton/ha/year of soil loss.
CA prevents desertification. This is important as the desertification is increasing in dry lands. Thereby, it reduces the socio-economic capacity of the rural population, because of deteriorated biomass-production. Hence conservation agriculture is important to develop capacity in the rural areas of the dry lands as it ensures increased yields (i.e. higher income)
Soil microbial activity is an indicator for soil fertility. Preliminary results showed that soil microbial activity was higher under CA than conventional practices for different studied soil layers (0-15 cm, 15-25 cm and 25-45 cm).
Regarding the impact of CA on natural resources, especially soil health and water efficiency. Scientific evidences show that soil loss due to erosion reduced by 14 percent, some 62 kilograms per hectare under CA practices compared to conventional practices.

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view	How can they be overcome?
The competition between livestock is identified as a major issue in terms of effectiveness and adoptability of conservation agriculture (CA). Livestock grazes the stubble and crop residues, reducing the amount of soil cover on the field, thus lowering the protection and improvement of the soil. And as most farmers rely on livestock, this conflict between livestock and CA lowers the adoption rate of the technology.	This can be addressed through integrated smart livestock management. The approach should aim at minimizing the harm to soil cover, while maximizing the nutrition intake of livestock. The 30/30-model, in which the optimal trade-off between soil cover and grazing period is found, offers such solution. Here 30 sheep or goats may graze one hectare for thirty days. This leaves enough soil cover and meets livestock demand.
The price and availability of the zero-tillage seeder is crucial in the farmer's decision to adopt CA. The purchase of such a machine is namely very high for a farmer. It is unlikely that a farmer is willing to invest this huge amount as the farmer prefers profit in the short term.	Investments (private and government) are needed to boost the manufacturing of national made zero-tillage seeder. This would increase the availability of the machine and decrease the price. Furthermore, farmers may organize themselves into communitiy user groups and cooperations hence, lowering the cost per farmer. However, good governance and planning of machine use is essential, as tension may develop during the short sowing period for the use of the machine.
The risks of pests and weeds increase during first years of the transition from conventional tillage to CA because of the residues left on the field and the change in the weeds flora. These form a good basis for disease development.	In the short term this can be overcome by using herbicides and fungicides. However, this might be paired with other risks. Therefore, there should be research into alternative pest controls measures, such as intercropping or the introduction of natural enemies.

Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view	How can they be overcome?
The low capacity of farmers to invest in CA, specifically a zero-tillage seeder, is a weakness. This is due to the lack of government support and due to the small scale of most farms (80% of the Tunisian farmers have less than 10 ha of land).	Iimprove institutional support by for example the government. The government can support farmers by giving subsides to allow the purchase of a zero-tillage seeder machine. The wider scale adoption of CA requires a change in commitment and behavior of all stakeholders. Such changes call for sustained policy and institutional support that provides both incentives and motivations to encourage farmers to adopt components of CA practices and improve them over time.
The increasing use of pesticides for weeding and pest control is a growing concern and risk. Pesticides may have harming effects on the soil, the biodiversity and the public health.	Alternatives to pesticides can overcome this risk. However, research is needed to scrutinize this and if it is cost-effective. Possible alternative approaches are intercropping and the introduction of natural enemies. This would not only mitigate the risk of pests and weeding, but also enhance soil health and biodiversity.

7.1 Methods/ sources of information

7.2 References to available publications

Title, author, year, ISBN:

Amir Souissi, Bahri Haithem, Hatem Cheikh M'hamed, Mohamed Chakroun, Salah Ben Youssef, Aymen Frija, Mohamed Annabi. (7/8/2020). Effect of Tillage, Previous Crop, and N Fertilization on Agronomic and Economic Performances of Durum Wheat (Triticum durum Desf. ) under Rainfed Semi-Arid Environment. Agronomy, 10(8).

Available from where? Costs?

https://hdl.handle.net/20.500.11766/11886

Title, author, year, ISBN:

Amar Rouabhi, Abdelmalek Laouar, Abdelhamid Mekhlouf, Boubaker Dhehibi. (1/3/2019). Socioeconomic assessment of no-till in wheat cropping system: a case study in Algeria. New Medit, 18(1).

Available from where? Costs?

https://hdl.handle.net/20.500.11766/9761

Title, author, year, ISBN:

Bahri Haithem, Mohamed Annabi, Hatem Cheikh M'hamed, Aymen Frija. (1/11/2019). Assessing the long-term impact of conservation agriculture on wheat-based systems in Tunisia using APSIM simulations under a climate change context. Science of the Total Environment, 692, pp. 1223-1233.

Available from where? Costs?

https://hdl.handle.net/20.500.11766/10157

Title, author, year, ISBN:

CLCA Project Page

Available from where? Costs?

https://mel.cgiar.org/projects/clca2

7.3 Links to relevant online information

Title/ description:

Zied Idoudi, Nasreddine Louahdi, Mina Devkota Wasti, Zahra Djender, Aymen Frija, Mourad Rekik. (26/4/2020). Public-Private Partnership for enhanced conservation agriculture practices: the case of Boudour Zero-Till seeder in Algeria. Lebanon: International Center for Agricultural Research in the Dry Areas (ICARDA).

URL:

https://hdl.handle.net/20.500.11766/11047

Title/ description:

Mourad Rekik, Santiago López Ridaura, Hatem Cheikh M'hamed, Zahra Djender, Boubaker Dhehibi, Aymen Frija, Mina Devkota Wasti, Udo Rudiger, Enrico Bonaiuti, Dina Najjar, Zied Idoudi. (26/11/2019). Use of Conservation Agriculture in Crop-Livestock Systems (CLCA) in the Drylands for Enhanced Water Use Efficiency, Soil Fertility and Productivity in NEN and LAC Countries – Project Progress Report: Year I - April 2018 to March 2019. Jordan: International Center for Agricultural Research in the Dry Areas (ICARDA).

URL:

https://hdl.handle.net/20.500.11766/10444

Title/ description:

Udo Rudiger, Hatem Cheikh M'hamed. (1/5/2019). Inspired by Nature - A Tunisian Farmer’s Perspective on Sustainable Integration of Crop and Livestock. (Short version).

URL:

https://hdl.handle.net/20.500.11766/10013

Title/ description:

Peter Fredenburg, Colin Piggin, Michael Devlin. (30/11/2012). Conservation agriculture: opportunities for intensified farming and environmental conservation in dry areas. Aleppo, Syria: International Center for Agricultural Research in the Dry Areas (ICARDA).

URL:

https://hdl.handle.net/20.500.11766/5073

Title/ description:

Hichem Ben Salem. (15/12/2015). Strategic Practical Options for Integrating Conservation Agriculture Cropping and Livestock Systems. Amman, Jordan: International Center for Agricultural Research in the Dry Areas (ICARDA).

URL:

https://hdl.handle.net/20.500.11766/4999

Title/ description:

Hichem Ben Salem. (4/5/2016). Recent trends in conservation agriculture.

URL:

https://hdl.handle.net/20.500.11766/4771

Title/ description:

Aymen Frija. (26/11/2016). Conservation Agriculture: strengthening crop production in marginal areas. URL: https://globalfutures.cgiar.org/2016/11/28/conservation-agriculture-strengthening-crop-production-in-marginal-areas/

URL:

https://hdl.handle.net/20.500.11766/6120

Title/ description:

Hajer Guesmi, Hichem Ben Salem, Nizar Moujahed. (1/9/2019). Integration crop-livestock under conservation agriculture system. Journal of New Science, 65(1), pp. 4061-4065.

URL:

https://hdl.handle.net/20.500.11766/11423

Title/ description:

Bahri Haithem, Mohamed Annabi, Hatem Cheikh M'hamed, Aymen Frija. (1/11/2019). Assessing the long-term impact of conservation agriculture on wheat-based systems in Tunisia using APSIM simulations under a climate change context. Science of the Total Environment, 692, pp. 1223-1233.

URL:

https://hdl.handle.net/20.500.11766/10157

Title/ description:

Ayoub Fouzai, Maroua Smaoui, Aymen Frija, Boubaker Dhehibi. (5/5/2019). Adoption of Conservation Agriculture Technologies by Smallholder Farmers in the semiarid region of Tunisia: Resource constraints and partial adoption. Journal of New Sciences, 6(1), pp. 105-114.

URL:

https://hdl.handle.net/20.500.11766/9988