Betula lenta (Black Birch, Sweet Birch)
Describes physical characteristics and provides photos of leaf, twig, flower, bark, and form.
http://www.cnr.vt.edu/dendro/dendrology/syllabus/blenta.htm

Betula papyrifera (Paper Birch, White Birch)
Information about habitat plus detailed description of leaves, flowers, and fruit. Photo included.
http://www.borealforest.org/trees/tree3.htm

Betula pendula (European Birch, White Birch)
Offers brief facts, including characteristics of leaf and fruit. Includes photos of entire tree, bark, and catkin.
http://www.oplin.org/tree/fact%20pages/birch_european/birch_european.html

Bowron Valley Log Homes
Custom log home builder offering handcrafted log homes and cabins as well as log fences and railings to finish your timber frame or log house
http://www.bowronvalleyloghomes.com

Adirondack White Birch
Adirondack White Birch: offers white birch bark, yellow birch twigs, yellow birch legs and birch tree bark for crafts, veneers, birch bark rustic furniture, baskets, ornaments, picture frames, candles and more.
http://adirondackwhitebirch.com/

Deneway Dollshouses
Beautiful hand built Georgian dollshouses in birch ply
http://denewaydollshouses.mysite.wanadoo-members.co.uk/

P.S. LAPORTE INC.
P.S. LAPORTE INC. : Notre compagnie se spécialise dans l'importation de contre-plaqué en provenance de Russie et d'Asie
http://www.pslaporte.com/

IPC Group
Manufacturers of birch plywood and other wood products from Russia.
http://www.birchplywood.com/

Betula populifolia (Gray Birch)
Images of the form of this tree.
http://www.treecanada.ca/trees/species_info.php?species_id=55&lang=en

Betulaceae
Describes the distinguishing characteristics of the birch family, comprising 6 genera.
http://www.botany.hawaii.edu/faculty/carr/betul.htm