Before revision:  A lot of methods have been proposed to address this problem which consists of the subtasks of (i) retrieving the relevant documents (and sentences) from Wikipedia and (ii) validating whether the information in the documents supports or refutes a given claim.
After revision:  A lot of methods have been proposed to address this problem which consists of the subtasks of retrieving the relevant documents (and sentences) from Wikipedia and (ii) validating whether the information in the documents supports or refutes a given claim.