This article incorporates text from a publication now in the public domain: Kellogg, Day Otis; Baynes, Thomas Spencer; Smith, William Robertson, eds. (1902). "Bekker, Elizabeth". The Encyclopaedia Britannica. Vol. 3. Werner. p. 511.
Brian Westerdale Downs and Henry Latimer Jackson (1921). A Manual of the Dutch Language. Cambridge University Press (Cambridge). p. 74.