c=1 Boundary Conformal Field Theory Revisited
  Correlation functions of discrete primary fields in the c=1 boundary conformal field theory of a scalar field in a critical periodic boundary potential are computed using the underlying SU(2) symmetry of the model. Bulk amplitudes are unambigously determined and we give a prescription for amplitudes involving discrete boundary fields. 
K. R. Kristjansson and L. Thorlacius