Classic texts: USDisp 1918.
Classic texts: King's 1898.
Henriette's herbal blog: They look a lot like hare droppings.
Henriette's herbal is one of the oldest and largest herbal medicine sites on the net. It's been online since 1995, and is run by Henriette Kress, a herbalist in Helsinki, Finland.
Plant Healer Magazine: Very relevant to the practitioner.
http://www.henriettes-herb.com - Copyright 1995–2015 Henriette Kress.