Bases of Feigin–Stoyanovsky’s type subspaces for C_l^(1)

In this paper, we construct combinatorial bases of Feigin–Stoyanovsky’s type subspaces of standard modules for level $k$ affine Lie algebra C_l^(1). We prove spanning by using annihilating field x_theta (z)^k+1 of standard modules. In the proof of linear independence, we use simple currents and intertwining operators whose existence is given by fusion rules.