Grofman, Bernard, Mikkel, Evald og Taagepera, Rein (2000). «Fission and fusion of parties in Estonia, 1987–1999». Journal of Baltic Studies(engelsk). 31 (4): 344 og 350. doi:10.1080/01629770000000141.CS1-vedlikehold: Flere navn: forfatterliste (link)
Fitzmaurice, John (2001). «The Parliamentary election in Estonia, March 1999». Electoral Studies(engelsk). 20 (1): 141–146. doi:10.1016/S0261-3794(00)00022-6.
Puusepp, Harrys, Kahar, Andres og Kamenik, Toivo m.fl. (red.) (2008). Annual Review 2007(PDF)(engelsk). Tallinn: Det estiske sikkerhetspolititet. s. 8. ISSN2228-1797. «[T]he main purpose of political intelligence manipulations of the Russian Foreign Intelligence Service (SVR) in 2007 was to ensure representation in the parliament (Riigikogu) of the Constitutional Party, supported and controlled from Russia.»CS1-vedlikehold: Flere navn: forfatterliste (link)
Puusepp, Harrys (red.) (2008). Annual Review 2019–2020(PDF)(engelsk). Tallinn: Det estiske sikkerhetspolititet. s. 14. ISSN2228-1797. «In the mid-2000s, the embassy tried its luck with the Constitution Party, formerly known as the Estonian United People’s Party. Its leaders used funds received from Russia for private purposes, failing to achieve a political breakthrough.»
Puusepp, Harrys, Kahar, Andres og Kamenik, Toivo m.fl. (red.) (2008). Annual Review 2007(PDF)(engelsk). Tallinn: Det estiske sikkerhetspolititet. s. 8. ISSN2228-1797. «[T]he main purpose of political intelligence manipulations of the Russian Foreign Intelligence Service (SVR) in 2007 was to ensure representation in the parliament (Riigikogu) of the Constitutional Party, supported and controlled from Russia.»CS1-vedlikehold: Flere navn: forfatterliste (link)
Puusepp, Harrys (red.) (2008). Annual Review 2019–2020(PDF)(engelsk). Tallinn: Det estiske sikkerhetspolititet. s. 14. ISSN2228-1797. «In the mid-2000s, the embassy tried its luck with the Constitution Party, formerly known as the Estonian United People’s Party. Its leaders used funds received from Russia for private purposes, failing to achieve a political breakthrough.»