Dyfyniad APA

Petroski, H. (1992). The pencil: A history of design and circumstance. New York: Alfred A. Knoff.

Dyfyniad Arddull Chicago

Petroski, Henry. The Pencil: A History of Design and Circumstance. New York: Alfred A. Knoff, 1992.

Dyfyniad MLA

Petroski, Henry. The Pencil: A History of Design and Circumstance. New York: Alfred A. Knoff, 1992.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.