Task: Question Understanding
Input (English): In this approach the similarity between two words is not strictly based on their co-occurrence frequencies, but rather on the frequencies of the other words which occur with both of them (i.e., second order co-occurrences). This approach has been shown to be successful in quantifying semantic relatedness BIBREF12 , BIBREF13 . 
 Question: What is a second order co-ocurrence matrix?
Output (English): Extractive