[1][2] He's best known for his research on the Kingdom of Sicily during the rule of king Frederick II of Hohenstaufen and the castle Castel del Monte.
His research focused mainly on the socioeconomic structure, the economic and agrarian development, the medieval fortification system and the institutions of Southern Italy in the Middle Ages.
[3][2] In his works (especially in Castel del Monte e il sistema castellare nella Puglia di Federico II), he also condemned the widespread esoteric views and interpretations on both the castle Castel del Monte and the king Frederick II himself, spread even by notable scholars and historians.
In particular, Licinio stressed that Castel del Monte was just one of the castles of the regional fortification system, and not a mysterious construction linked to the Knights Templar.
His testimony also helped to identify the murderer of Benedetto Petrone, who had been stabbed to death in Bari on November 28, 1977, by a gang of neo-fascists.