1. ASTM D 6243. Standard Test Method for Determining the Internal and Interface Shear Resistance of Geosynthetic Clay Liner by the Direct Shear Method. American Society for Testing and Materials International West Conshohocken PA USA.
2. ASTM D 6496. Standard Test Method for Determining Average Bonding Peel Strength Between the Top and Bottom Layers of Needle-Punched Geosynthetic Clay Liners. American Society for Testing and Materials International West Conshohocken PA USA.
3. Berard J. F. (1997). "Evaluation of needle punched geosynthetic clay liners' internal friction". Proc. Geosynthetics 1997 IFAI Long Beach CA Vol. 1: 351-362.
4. Internal and interface shear strengths of unreinforced and needle-punched geosynthetic clay liners
5. Effect of Shear Displacement Rate on Internal Shear Strength of a Reinforced Geosynthetic Clay Liner