Luciano Gualà; Stefano Leucci; Emanuele Natale (24 March 2014). "Bejeweled, Candy Crush and other Match-Three Games are (NP-)Hard". arXiv:1403.5830. Bibcode:2014arXiv1403.5830G. {{cite journal}}: Cite journal requires |journal= (help)
casualcharts.com
Juul (2009) p. 100; making reference to data from casualcharts.com for the "match3" and "chainpopper" mechanics as tracked by "popular portals" (footnote 52)