Humbert, F. L. (1968). Selection and wear of pebbles on gravel beaches.
Lua i Stíl Chicago (17ú heag.)Humbert, Fekko Lucas. Selection and Wear of Pebbles on Gravel Beaches. [Groningen, 1968.
Lua MLA (8ú heag.)Humbert, Fekko Lucas. Selection and Wear of Pebbles on Gravel Beaches. 1968.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.