TY  - BOOK
AU  - Koch,Helen L.
TI  - Twins and twin relations / 
U1  - 155.444 
PY  - 1966///
CY  - Chicago : 
PB  - The University of Chicago Press, 
KW  - Twins
KW  - Psychology
N1  -  Includes bibliographical references (p.281-292) and index
ER  -