APA Style
Penwell, Directories. (1989).
WORLDWIDE REFINING & GAS PROCESSING DIRECTORY, 1990 Edition .
United States of America:
PennWell Publishing Company.
Chicago Style
Penwell, Directories.
WORLDWIDE REFINING & GAS PROCESSING DIRECTORY, 1990 Edition.
United States of America:
PennWell Publishing Company,
1989.
Text.
MLA Style
Penwell, Directories.
WORLDWIDE REFINING & GAS PROCESSING DIRECTORY, 1990 Edition.
United States of America:
PennWell Publishing Company,
1989.
Text.
Turabian Style
Penwell, Directories.
WORLDWIDE REFINING & GAS PROCESSING DIRECTORY, 1990 Edition.
United States of America:
PennWell Publishing Company,
1989.
Print.