1. Die Nissbildungen des Menschen;Ashfeld,1880
2. A case of supernumerary testis;Lane;Trans. Clin. Soc., Lond.,1895
3. Polyorchidism;Broggan;Brit. J. Urol.,1933
4. Two testicles on one side;Marsh;Brit. Med. J.,1911
5. Duplication of the testis and infertility;Jichlinski;J. Urol.,1963