CHABAKOV, A.W. (1927)
O nachodke w kamennougolnych otloshenijach SSSR jajzewych kapsul elasmobranchij Palaeoxyris i Vetacapsula. (About the find of elasmobranch egg capsules from Carboniferous deposits of the USSR) [In Russian] Westnik geologitscheskogo komiteta, 1: 33–34