Torah Trivia II

It is well-known that the Frankel edition of the Mishneh Torah used political considerations in determining what to exclude from its index of sources. That is why Modern Orthodox and Lubavitch sources are not cited. However, I found one place in which a work of R. Yosef Dov Soloveitchik is quoted. In the "sefer ha-mafte'ah" to Hilkhos Melakhim 5:5, it refers to R. Moshe Soloveitchik as cited in Be-Sod Ha-Yahid Ve-Ha-Yahad, p. 392 (a work by his son, R. Yosef Dov).