Bookbird: A Journal of International Children's Literature , Vol. 55, No. 3, 2017, pp. 34–41.
Dr. Mareike O. Späth (University of Bonn) ruby red series
Here’s a useful academic paper on the Ruby Red trilogy: “Time, Gender, and Identity in Kerstin Gier’s Ruby Red Trilogy” Bookbird: A Journal of International Children's Literature ,