  In modern terminology, this is the first published paper where the solutions
of Yang - Baxter equation "at roots of unity" were analyzed and shown to be
related to algebraic curves of genus >1. They are also known now to be
connected with the "chiral Potts model". The paper's abstract as written in
1986 reads: "Vacuum vectors of an L-operator form a holomorphic bundle over the
vacuum curve of that operator. These notions, as well as the theory of
commutation relations of the 6-vertex model, are used in this work for
constructing solutions of the Yang - Baxter equation that do not possess a
spectral parameter of traditional type".
