[1]
A. V. Shavrina, Y. V. Glagolevskij, J. Silvester, G. A. Chuntonov, Y. V. Pavlenko, і V. R. Khalack, «SPOTS STRUCTURE AND STRATIFICATION OF SOMECHEMICAL ELEMENTS IN THE ATMOSPHERE OF He-WEAK STAR HD 21699», Одес. астроном. публ., т. 21, с. 115–119, Груд 2008.