This note refers to the following paper:

M. Heilman, K. Collins-Thompson, J. Callan, and M. Eskenazi. 2007. Combining lexical and grammatical features to improve readability measures for first and second language texts. In Proc. of NAACL-HLT.

In section 3.2, the interpolation equation is incorrect in that it does not reduce the contribution of the language model component. The equation should be: L_interpolated = (L_languagemodel + C_kNN * L_grammar) / (1 + c_kNN). ---Michael Heilman

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