Cita APA (7th ed.)

Krebs, R. D., & Walker, R. D. (1971). Highway materials. McGraw-Hill.

Cita Chicago (17th ed.)

Krebs, Robert D., i Richard D. Walker. Highway Materials. New York: McGraw-Hill, 1971.

Cita MLA (9th ed.)

Krebs, Robert D., i Richard D. Walker. Highway Materials. McGraw-Hill, 1971.