Birch bark

bark of several Eurasian and North American birch trees of the genus Betula

document written on pieces of the inner layer of birch bark

group of mathematical manuscripts including an early use of the positional zero

Betulin is an abundant, naturally occurring triterpene. It is commonly isolated from the bark of birch trees, hence its name, from betula. It forms up to 30% of the dry weight of silver birch bark. It is also found in birch sap. Inonotus obliquus contains betulin.

Ancient Buddhist texts

oldest document in any Finnic language