Pritchet, Christopher J.; Van Den Bergh, Sidney (1987). ”Observations of RR Lyrae stars in the halo of M31” (på engelska). Astrophysical Journal 316: sid. 517. doi:10.1086/165223.
”RR Lyrae Variables in the Globular Clusters of M31: A First Detection of Likely Candidates” (på engelska). The Astrophysical Journal 559 (2): sid. L109. 2001. doi:10.1086/323973.