Cita APA (7th ed.)

Perko, H. A. (2009). Helical piles: A practical guide to design and installation. John Wiley & Sons.

Cita Chicago (17th ed.)

Perko, Howard A. Helical Piles: A Practical Guide to Design and Installation. Hoboken, NJ: John Wiley & Sons, 2009.

Cita MLA (8th ed.)

Perko, Howard A. Helical Piles: A Practical Guide to Design and Installation. John Wiley & Sons, 2009.