Medieval literature
Hercoginja's research interest focuses on Croatian Middle Ages. His "Srednjovjekovna književnost" ('Medieval literature') in »Liber's« edition "Povijest hrvatske književnosti" ('The history of Croatian literature'; Volume II, Zagreb 1975), based on extensive textological, linguistic and historical research of Glagolitic heritage, has managed to paint a different picture of medieval Croatian texts as what used to be called a 'precursor of literature' (A. Cronia).