TY  - BOOK
AU  - Erdos,Renâee F.
TI  - Teaching by correspondence: 
PY  - 1967///
CY  - London, ,  Paris, , Paris, , Paris, , Paris, 
PB  - Longmans; ,  Unesco, , Unesco, , Unesco, , Unesco, 
KW  - Correspondence schools and courses
N1  -  Bibliography: p. 213-214
ER  -