  We investigate the similarities of pairs of articles which are co-cited at
the different co-citation levels of the journal, article, section, paragraph,
sentence and bracket. Our results indicate that textual similarity,
intellectual overlap (shared references), author overlap (shared authors),
proximity in publication time all rise monotonically as the co-citation level
gets lower (from journal to bracket). While the main gain in similarity happens
when moving from journal to article co-citation, all level changes entail an
increase in similarity, especially section to paragraph and paragraph to
sentence/bracket levels. We compare results from four journals over the years
2010-2015: Cell, the European Journal of Operational Research, Physics Letters
B and Research Policy, with consistent general outcomes and some interesting
differences. Our findings motivate the use of granular co-citation information
as defined by meaningful units of text, with implications for, among others,
the elaboration of maps of science and the retrieval of scholarly literature.
