Much of her work is the analysis and publication of historical sources. Relying partly on the contributions of earlier historians, she analyzed the entire Croatian diplomatic material of the Early Middle Ages ("Diplomatic Analysis of the Documents from the Age of Croatian Rulers of Croat Descent", 1965, 1966–67), questioning its authenticity. Along with the anonymous Split chronicle called "Historia Salonitana maior" (1967), Klaić published several sources translated from Latin for the needs of students ("Sources for Croatian History before 1526", 1972).