Samples of Kantele Music
https://www.kantelemusic.com/music.html
Sources:
https://www.etymonline.com/word/birch
https://www.etymonline.com/word/betula
https://plants.ces.ncsu.edu/plants/betula-lenta/
https://www.blackhillsbadlands.com/blog/2011-07-21/aspen-birch-distinguishing-differences
https://www.thespruce.com/twelve-species-cultivars-of-birch-trees-3269660
http://www.chinadaily.com.cn/china/2017-10/12/content_33148913.htm
http://www.thebirchonline.org/about-us/
http://www.uwosh.edu/coehs/cmagproject/ethnomath/legend/legend10.htm
https://renegadebrewing.com/birch-beer-vs-root-beer/
https://www.herballegacy.com/Birch_History.html
https://www.deccanherald.com/content/214209/kashmir-source-birch-bark-used.html
http://www.ecoenchantments.co.uk/myogham_birchpage.html
https://www.absolutely-wild.com/images/uses-of-tree-sap-in-europe.pdf
https://ouroneacrefarm.com/2014/01/12/wintergreen-extract-birch/
https://www.hbgf.org/blog/garden-word-lenticel
The Kalevala by Elias Lönnrot, Canto 44