C. Fowler
发表
W. A. Myers,
R. L. Shoff,
W. F. Herndon,
1958
.
Bjarne Stugu,
Francesca Campabadal,
O. K. Øye,
2007
.
Helmuth Spieler,
Bjarne Stugu,
Takashi Kohriki,
2005
.