TY  - BOOK
AU  - Keyfitz Nathan
AU  -  Beekman John A
TI  - Demography through problems
T2  - Problems books in mathematics
U1  - Y:5, M4-;2 
PY  - 1984///
CY  - New York    
PB  -  Springer Verlag       
KW  -  Populations
KW  - Demography
ER  -