^(EN) Awards of the Donohoe Comet-Medal, Publications of the Astronomical Society of the Pacific, vol. 19, n. 116, pag. 236, ottobre 1907
^(EN) Awards of the Donohoe Comet-Medal, Publications of the Astronomical Society of the Pacific, vol. 20, n. 119, pag. 93, aprile 1908
^(EN) Campbell, W. W.; Tucker, R. H.; Curtis, Heber D., (Eighty sixth) Award of the Donohoe Comet-Medal, Publications of the Astronomical Society of the Pacific, vol. 28, n. 163, pag. 76, aprile 1916
^(EN) Campbell, W. W.; Tucker, R. H.; Curtis, Heber D., (Eighty seventh) Award of the Donohoe Comet-Medal, Publications of the Astronomical Society of the Pacific, vol. 28, n. 163, pag. 77, aprile 1916