1. A. Scheurer-Kestner, “Theoretical Considerations on the Preparation of NaOH by the Leblanc Process,≓C.R. Hebd. Séances Acad. Sci., 57,1013–1016 (1863) in French. (Equi Diagram; Experimental)
2. M. Sabatier, “Thermochemical Measurements on Sulfides,≓Ann. Chim. Phys. Sth Ser., 22, 5–98(1881)in French. (Equi Diagram, Thermo ; Experimental)
3. J. Locke and A. Austell, “The Effect of S on Metallic Na,≓Am. Chem. J., 20(1), 592–594 (1898). (Equi Diagram; Experimental)
4. C. Hugot, “Action of Na and K on Te and S in Liquid Ammonia,≓C.R. Hebd. Séances Acad. Sci., 129, 388–391 (1899) in French. (Equi Diagram; Experimental)
5. W.P. Bloxam, “Hydrosulfides, Sulfides and Polysulfides of K and Na,≓Trans. Chem. Soc., 77,753–770 (1900). (Equi Diagram; Experimental)