Giffen, R., Higgs, H., & Yule, G. U. (1913). Statistics. Macmillan and Co..
Lua i Stíl Chicago (17ú heag.)Giffen, Robert, Henry Higgs, agus G. Udny Yule. Statistics. London: Macmillan and Co., 1913.
Lua MLA (8ú heag.)Giffen, Robert, et al. Statistics. Macmillan and Co., 1913.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.