TY  - BOOK
AU  - Singh,H.S., x
AU  - x
TI  - Principles of environmental conservation: x
SN  - 8770891019
U1  - 628.5/S617p 
PY  - 1989///
CY  - Dehra Dun
PB  - International Book Distributors
KW  - Environment
KW  - Pollution
N1  - x
ER  -