The assimilation *d-g- > *g-g- in Slavic probably have spread from the 0-grade forms, which created a similar environment to the so-called thorn clusters in Proto-Indo-European. Compare the descendants of Proto-Indo-European*dʰgʷʰey-(“to dwindle, to perish”).
Vasmer, Max (1964–1973), “жгу”, in Oleg Trubachyov, transl., Этимологический словарь русского языка [Etymological Dictionary of the Russian Language] (in Russian), Moscow: Progress
Chernykh, P. Ja. (1999), “жечь”, in Историко-этимологический словарь русского языка [Historical-Etymological Dictionary of the Russian Language] (in Russian), 3rd edition, volume 1 (а – пантомима), Moscow: Russian Lang., →ISBN, page 301
Georgiev, Vladimir I., editor (1971), “жег”, in Български етимологичен речник [Bulgarian Etymological Dictionary] (in Bulgarian), volume 1 (А – З), Sofia: Bulgarian Academy of Sciences Pubg. House, →ISBN, page 529
^ Derksen, Rick (2008), “*žegti”, in Etymological Dictionary of the Slavic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 4), Leiden; Boston: Brill, →ISBN, page 554: “v. (c) ‘burn’”
^ Derksen, Rick (2015), “degti”, in Etymological Dictionary of the Baltic Inherited Lexicon (Leiden Indo-European Etymological Dictionary Series; 13), Leiden, Boston: Brill, →ISBN, page 119: “*žegtì v. (c) ‘burn’”
^ Olander, Thomas (2001), “žegti: žegǫ (žьgǫ) žežetь”, in Common Slavic Accentological Word List[1], Copenhagen: Editiones Olander: “c brænde (PR 139)”
^ Snoj, Marko (2016), “žgáti”, in Slovenski etimološki slovar [Slovenian Etymology Dictionary] (in Slovene), 3rd edition, https://fran.si: “*žet'i̋”
↑ 5.05.1Rejzek, Jiří (2015), “žhnout”, in Český etymologický slovník [Czech Etymological Dictionary] (in Czech), 3rd (revised and expanded) edition, Praha: LEDA, →ISBN, page 818
