1. Gravel envelope design and construction at the Fourth Drainage Project, Pakistan;Bhatti,1989
2. Subsurface PVC pipes envelopes design and research;Dierickx,1989
3. Comparative study of the East Khairpur, Mardan and Drainage IV pipe drainage projects;IWASRI,1990
4. Synthetic drain envelope; scenario for use in Pakistan;IWASRI,1990
5. Comparison of three subsurface pipe drainage projects in Pakistan;Vlotman,1990