TY  - BOOK
AU  - Zimmerman, H. J.
TI  - Fuzzy set theory : and it's applications .-4th ed .-978-81-8128-519-5
SN  - 978-81-8128-519-5
U1  - 511.3 Zim 
PY  - 2001///
CY  - Springer, New Delhi
ER  -