"2-Letter Words with Definitions". Australian Scrabble Players Association (ASPA). 8 May 2007. Archived from the original on 5 March 2013. Retrieved 20 February 2013.
Everson, Michael; Baker, Peter; Emiliano, António; Grammel, Florian; Haugen, Odd Einar; Luft, Diana; Pedro, Susana; Schumacher, Gerd; Stötzner, Andreas (January 30, 2006). "L2/06-027: Proposal to add Medievalist characters to the UCS"(PDF). Archived(PDF) from the original on September 19, 2018. Retrieved March 24, 2018.
"2-Letter Words with Definitions". Australian Scrabble Players Association (ASPA). 8 May 2007. Archived from the original on 5 March 2013. Retrieved 20 February 2013.
Everson, Michael; Baker, Peter; Emiliano, António; Grammel, Florian; Haugen, Odd Einar; Luft, Diana; Pedro, Susana; Schumacher, Gerd; Stötzner, Andreas (January 30, 2006). "L2/06-027: Proposal to add Medievalist characters to the UCS"(PDF). Archived(PDF) from the original on September 19, 2018. Retrieved March 24, 2018.