TY  - BOOK
AU  - WILLIAM GRAVES, EDITOR ETC.
TI  - NATIONAL GEOGRAPHIC APRIL 1993
T2  - VOL. 183 NO.4 1993
U1  - 050.8 NG v.04 1993 
PY  - 1993///
CY  - 
PB  - NATIONAL GEOGRAPHIC SOCIETY
KW  - 连续性出版品; 期刊--NATIONAL GEOGRAPHIC
ER  -