TY  - BOOK
AU  - Meyer,Richard F.
AU  - De Witt,Wallace
ED  - United States
TI  - Definition and world resources of natural bitumens
U1  - 553.24 
PY  - 1990///].
CY  - [Washington]: 
PB  - [United States Government Printing Office], 
KW  - Bitumen
KW  - Asphalt
N1  - Includes bibliographical references (p. 13-14)
N2  - Definitions of the main types of natural bitumens, with emphasis on natural asphalt, the most significant quantitatively and economically, and its world distribution
ER  -