1. Über die Polarisation des Lichtes des Crab-Nebels;Chatschikjan;DAN Arm. SSR,1955
2. Observed changes in the structure of the “Crab” nebula (NGC 1952);Lampland;Publ. Astron. Soc. Pac.,1921
3. Polarization and composition of the Crab nebula;Oort;Bull. Astron. Inst. Netherlands,1956
4. Détermination de la polarisation de la couronne solaire;Fessenkow;Astron. J. UdSSR,1935
5. Result of application of focus plate holder in surface photometry of nebula;Markow;C. R. Academie des Sciences de U.S.S.R.,1933