Whittaker, E. (1 de novembro de 1955). «Albert Einstein. 1879-1955». Biographical Memoirs of Fellows of the Royal Society. 1: 37–67. doi:10.1098/rsbm.1955.0005
«An elementary proof of the theorem concerning the equivalence of mass and energy». Bull. Amer. Math. Soc. 31 (4): 223–230. 1935. doi:10.1090/s0002-9904-1935-06046-x
Christopher E., Spratt (1990). «The Hungaria group of minor planets». Journal of the Royal Astronomical Society of Canada (em inglês). 84 (2): 123–131. Bibcode:1990JRASC..84..123S