In order to reflect the idea of bidirectional context in the proposed model, the model is enhanced by modifying È´Û ½ Û Ý µ in Equation (1).
the likelihood of È´Û ½ Û Ý µ is expanded to Since the coefficients of Equation (4) were determined arbitrarily (Kang, 2004), they are replaced with parameters « of which values are determined using a held-out data.