-
V. V. Shokurov, “Complements on surfaces”, J Math Sci, 102:2 (2000),
3876 
-
YURI G. PROKHOROV, “BOUNDEDNESS OF NONBIRATIONAL EXTREMAL CONTRACTIONS”, Int. J. Math., 11:03 (2000),
393 -
D. G. Markushevich, Yu. G. Prokhorov, “Klein's group defines an exceptional singularity of dimension 3”, J Math Sci, 94:1 (1999),
1060