http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0101298
cites Ullmann's Encyclopedia of Industrial Chemistry
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0020160
cites The Cambridge Encyclopedia of Language
http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0003955
Cites The Tennessee Encyclopedia of History and Culture.