封筒
http://www.keysan.com/big/picequa0385.html
http://www.belightsoft.com/products/companion/paper/envelopes.php
http://www.envelopesexpress.com/cat_type.asp?page=Commercial&type=Regular
http://www.thepapermillstore.com/
http://www.envelopemall.com/
http://www.actionenvelope.com/
http://www.artpaper.com/vellum_envelopes.html