[1] Political and commercial correspondence between different courts in the medieval era was mediated by scribes, each of whom was responsible for communication in one specific language.
He may not have been originally a scribe but someone who was considered trustworthy as in his writing he changed the spelling of his name several times and didn't call himself a logotet as was customary.
[2] He wrote his surname as Vlkosalik and Vukosalik (Вꙋкосалик); the modern spelling is Vukosalić.
In the first letter, he calls himself a dijak (scribe) which he continues to use in later correspondence but later also adopts the commonly recognized title of chancelier in Ragusa.
[5] The letters written by Ninac were published in the late 19th century by Franz Miklosich.