(1999) World Music: Africa, Europe and the Middle East. The Rough Guide, გვ. 16, 19–20 and 24. ISBN978-1858-2863-5-8. „Baltic psalteries variously called kantele, kannel, kokles or kanklės. (..) Kokles and citara. (...) The Latvian Baltic zither is called the kokle or kokles (...) it's usual to tune the lowest string of a kokles to a drone a fourth below the key note.“
Peddie, Ian (2016). Popular Music and Human Rights: Volume II: World Music. Routledge, გვ. 74, 82. ISBN9781317078180. „folk music instrument orchestras, and kokles ensembles (...) numerous kokle ensembles as well. The whole modernized kokle family (...) included appearance of kokle players“
(2017) The Garland Encyclopedia of World Music: Europe. Routledge, გვ. 170, 503–504, 505. ISBN978-1351-5442-6-9. „The most characteristic and significant instrument in Latvian traditional music is the kokles, a board zither with five to twelve strings. (...) Small plucked zithers include the langeleik (Norway), the kantele (Finland), the kannel (Estonia), the kanklės (Lithuania), and the kokles (Latvia).“
O'Connor, Kevin (2006). Culture and Customs of the Baltic States. Greenwood Publishing Group, გვ. 176–177. ISBN978-0313-3312-5-1. „The most popular Baltic folk instrument is the board zither (psaltery), known as the kannel in Estonian, the kokles in Latvia and the kanklės in Lithuania. (..) the early kannel-kokles-kanklės was a five stringed instrument“
Peddie, Ian (2016). Popular Music and Human Rights: Volume II: World Music. Routledge, გვ. 74, 82. ISBN9781317078180. „folk music instrument orchestras, and kokles ensembles (...) numerous kokle ensembles as well. The whole modernized kokle family (...) included appearance of kokle players“
Djupsjöbacka, Tove. (May 24, 2016) The kantele – not exclusively Finnish. Finnish Music Quarterly. ციტატა: „The official status of kanteles varies from one country to another. In the Baltic states, these instruments (the kannel in Estonia, the kokles in Latvia and the kanklės in Lithuania) have a firm official status.“ ციტირების თარიღი: May 24, 2017
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Muktupāvels, Valdis. (1999)Systematics of Latvian musical instruments lv გვ. 96, 100–101. Latvijas Mākslas augstskolu asociācija. ციტატა: „Kokles, kokle (K; Z; V), kūkles (L), kūkle (L)“ ციტირების თარიღი: March 30, 2017[მკვდარი ბმული]