As ∑ y α y is too large to be ignored, especially when the frequency n(x) is small, Equation (4) shows that the maximum likelihood estimationp y | x estimates the probability to be excessively large.
we propose using Kneser-Ney smoothing (Kneser and Ney, 1995), which is considered to be an extension of the Dirichlet smoothing above, to mitigate overestimation of paraphrase probability in bilingual pivoting.