KREBS, R. D., & WALKER, R. D. (1971). Highway materials. McGraw-Hill.
Lua i Stíl Chicago (17ú heag.)KREBS, Robert D., agus Richard D. WALKER. Highway Materials. New York: McGraw-Hill, 1971.
Lua MLA (9ú heag.)KREBS, Robert D., agus Richard D. WALKER. Highway Materials. McGraw-Hill, 1971.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.