Characteristics of pairs by difficulty class. Characteristics of pairs by difficulty class (average sentence length in words, average word distance between entities, average distance in the dependency graph (DG) and syntax tree (ST) shortest path). ND – negative difficult, NN – negative neutral, NE – negative easy, PD – positive difficult, PN – positive neutral, PE – positive easy.
Tikk et al. BMC Bioinformatics 2013 14:12 doi:10.1186/1471-2105-14-12