Lilly, W. E. (1921). Discussion on hardness testing.
Lua i Stíl Chicago (17ú heag.)Lilly, W. E. Discussion on Hardness Testing. 1921.
Lua MLA (9ú heag.)Lilly, W. E. Discussion on Hardness Testing. 1921.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.
