I woudn't say that Italian official historiography has really emphasized this fact - at least since 1943. Rather, it has consistently attempted to place the "Adriatic question" in its proper context and to attribute to it its correct historical significance.

For references, see Vivarelli, R. - Storia delle origini del Fascismo; Valiani, L. - La dissoluzione dell'Austria-Ungheria; Alatri, P. - Nitti, D'Annunzio e la questione Adriatica; De Felice, R. - Mussolini and Sindacalismo rivoluzionario e Fiumanesimo; Pupo, R. - Fiume, città di passione; Isnenghi, M. - Ritorni di Fiamma; Salvemini, G. Maranelli, C. - La questione dell'Adriatico.

For works of a different persuasion one needs to look back to the more or less "official" pubblications of the 1920s and 1930s - both hagiographies or memoirs related to the "Fiume Enterprise" (Coselschi, Benedetti, Giannini, Susmel, etc.) and general reviews of the Adriatic question (for instance Federzoni). Of some significance is the elaboration concerning the diplomatic side of the Adriatic question - especially the works of M. Toscano on the Treaty of London, but also memoirs such as the ones from Crespi and the transcriptions of Aldrovandi-Marescotti.

I have written with some largeness on the history, significance and ideas surrounding the Italian diplomatic position in 1919 and the events of Fiume. While not in depth with regards to the outlook of other nations, these could represent a starting point: one with summary of other posts, two for a brief summary of the Italian situation

 

Edit: and I fogot to mention /u/quiaudetvincet who also provided an answer in the first of the two linked posts!

Additionally, while I think there is a somewhat extensive coverage (at least of the Italian side of things) in those threads I linked, I didn't mean to imply that you shouldn't ask more specific questions if something appears unclear.