Russi Georgiev Yordanov
+359 2 8161-546
Note: Parts of refs. 1, 10 and 12 above have also been included in a book written by my ex-advisor E. Khristov et al, "Spectral Methods in Soliton Equations", Pitman Monographs and Surveys in Pure and Applied Mathematics, # 73 (see Secs. 3.10, 3.11 and 3.A there).