“…Based on the work of Matveev, Smirnov, Previato and McKean in the reduction theory of Riemann theta functions [30,31,36,39,32,2], Dickson and his collaborators proposed a unified framework which yields all algebro-geometric quasi-periodic solutions of the entire Boussinesq hierarchy related to the third-order operator [9,10]. Recently, this method was successfully generalized to solve soliton equations associated with 3 × 3 matrix spectral problems such as the modified Boussinesq, the Kaup-Kupershmidt, the coupled modified Korteweg-de Vries and the three-wave resonant interaction hierarchies based on the trigonal curves introduced by the characteristic polynomials of the Lax matrices [17,18,20,24]. In order to solve finite genus solutions of the coupled Sasa-Satsuma hierarchy, we shall introduce a trigonal curve with the aid of the Lax matrix.…”