<Dd> Stores a list of occurrences of each atomic search criterion, typically in the form of a hash table or binary tree . </Dd> <Dl> <Dt> Citation index </Dt> <Dd> Stores citations or hyperlinks between documents to support citation analysis, a subject of Bibliometrics . </Dd> <Dt> Ngram index </Dt> <Dd> Stores sequences of length of data to support other types of retrieval or text mining . </Dd> <Dt> Document - term matrix </Dt> <Dd> Used in latent semantic analysis, stores the occurrences of words in documents in a two - dimensional sparse matrix . </Dd> </Dl> <Dd> Stores citations or hyperlinks between documents to support citation analysis, a subject of Bibliometrics . </Dd> <Dd> Stores sequences of length of data to support other types of retrieval or text mining . </Dd>

Search engines like google cannot index what types of information