Among his other works (all in Russian) are a popular science book «К истокам слова» ("The origins of speech" – 4 successive editions) ; collections of articles «Opera philologica minora», and «Очерки по этимологии» ("Essays on etymology"); monographs «Карийские надписи Африки» ("Carian inscriptions in Africa" [1966]), and "Фестский диск: Проблемы дешифровки" (Phaistos disk: the problems of decipherment).
In his book, he was trying to justify his point of view using the analysis of Carian names and onomastics, as well as using other linguistic evidence as preserved in Greek texts.
Also, according to him, his attempt to read newly discovered Carian inscriptions in Egypt gave him additional supporting evidence.
Nevertheless, the questions remain whether or not Otkupshchikov managed to identify the genuine Carian element in all that ancient material or, rather, that his cases may also represent an adstrate brought in by Paleo-Balkan infiltrations.
[4][5] He believed that: "... Greek is genetically close to a group of related Paleo-Balkan languages, whose speakers lived in the northeastern part of the Balkan Peninsula... Later on, the ancestors of the Carians, Phrygians and Thracians, in several waves and at different times, moved to the south of the Balkan Peninsula and ... Indo-Europeanized a non-Indo-European culture, borrowing a significant amount of non-Indo-European vocabulary.
However, the majority of Phrygians and Thracians moved not to the south, but to the southeast - to Asia Minor (along the path laid by the Armenians) ...