1. Lenssen, E.: J. Prakt. Chem. 78, 193 (1859)
2. Benas, T.: Chem. Zentralblatt, 15, 957 (1884)
3. Borgman, P.J.S.: Chem. Zentralblatt 8, 212 (1896)
4. Crookes, W.: Select Methods in Chemical Analysis, London, Longman, 1871
5. Parry, L.: The Assay of Tin and Antimony, London, Mining Journal Office 1906