Abelian functions for trigonal curves of degree four and determinantal   formulae in purely trigonal case
  This paper gives a natural extension of Frobenius-Stickelberger formula and Kiepert formula to Abelian functions for "Purely Trigonal Curves", especially, of degree four. A description on the theory of Abelian functions for general trigonal curves of degree four is also included. 
Yoshihiro \^Onishi