[1971, BAC 22, 87; 1975, BAC 26, 90; 1978, IAUC 3317; 1988, IBVS No. 3263; 1989, Sp. Sc. Rev. 50, 365; IBVS No. 3386; 1990, BAC 41, 29; 1991, BAC 42, 230; 1994, A&A 105, 119; IAU Symp. 162, p.301; 1996, A&A 309, 521; A&A 312, 879; A&A 315, L401; 1997, A&A 319, 867; A&A 322, 565; A&A 324, 965; A&AS 125, 75; A&A 328, 551; JAD No.3]