Marcus, Ralph. "The Sebomenoi in Josephus". Jewish Social Studies. 14 (3). Indiana University Press. ss.247-250. JSTOR4465081. We know from Pagan, Christian and Jewish sources that during the Hellenistic and early Roman periods some Gentiles were so strongly attracted to Judaism that they became converts and undertook to observe Jewish laws and customs in the same manner as did the Jews themselves. [...] It is also commonly assumed that there were some Gentiles who did not go so far as to become converts but indicated their belief in monotheism and gave up the worship of Pagan gods. How far they went in openly dissociating themselves from Paganism and in associating themselves with Judaism we do not know. These Gentile sympathizers are commonly thought to be referred by the terms sebomenoi or phoboumenoi ton theon and metuentes in Greek and Latin sources, and yir᾿ê shamayim "fearers of Heaven" (i.e. God-fearers) in some early Rabbinic passages.
Bromiley, Geoffrey W. (1986). The International Standard Bible Encyclopedia. 3 (Fully Revised bas.). Grand Rapids, Michigan: Eerdmans. s.1010. ISBN0-8028-3783-2. Many scholars see a parallel between the "God-fearers" in rabbinic literature and the "God-fearers" in the NT. In rabbinic literature the ger toshab was a Gentile who observed the Noachian commandments but was not considered a convert to Judaism because he did not agree to circumcision. [...] some scholars have made the mistake of calling the ger toshab a "proselyte" or "semiproselyte." But the ger toshab was really a resident alien in Israel. Some scholars have claimed that the term "those who fear God" (yir᾿ei Elohim/Shamayim) was used in rabbinic literature to denote Gentiles who were on the fringe of the synagogue. They were not converts to Judaism, although they were attracted to the Jewish religion and observed part of the law.
Trebilco, Paul (2001). "I «Timorati di Dio»". Lewin, Ariel (Ed.). Gli ebrei nell'Impero romano: saggi vari (İtalyanca). Floransa: La Giuntina. ss.161-193. ISBN88-8057-120-6.