APA (7th ed.) Citation

O'Hara, A. (1999). A practical guide to gas contracting. PennWell Books.

Chicago Style (17th ed.) Citation

O'Hara, Ann. A Practical Guide to Gas Contracting. Tulsa, OK: PennWell Books, 1999.

MLA (9th ed.) Citation

O'Hara, Ann. A Practical Guide to Gas Contracting. PennWell Books, 1999.

Warning: These citations may not always be 100% accurate.