TY  - BOOK
AU  - Johnson, David E.
TI  - Introduction to filter theory
T2  - Prentice-hall electrical engineering series
SN  - 0-13-483776-2
U1  - D66e,2 L6J 
PY  - 1976///
PB  - Prentice-Hall
KW  - Electric filters
N1  - Includes appendix, bibliography and index
ER  -