55–56; tsepenkov 1972, p. 9. (Folk beliefs. Children's games), p. 45; aiF, zbirka 10, “obichai okolu radianie, sklopuvanie braki umirachka vo osogoviia” (aiF, Collection no. 10, Customs related to birth, marriage and death in Osogoviia region).
Gábor Klaniczay, Éva Pócs, 2006