Gaya APA
Pennwell, .
(2003).
Oil & Gas Journal, Opec,s new Challenger
(
Week of July 2003)
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Houston:
Pennwell Books.
Gaya MLA
Pennwell, .
"Oil & Gas Journal, Opec,s new Challenger".
Week of July 2003
Houston:
Pennwell Books,
2003.
Jurnal TP.