Classic texts: Eli Jones' Definite Medication, 1911.
Henriette's herbal blog: The aboveground parts of mullein are covered in itchy hairs.
Classic texts: Ellingwood 1910.
Classic texts: Journals: Ellingwood 1908.
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 1995–2016 Henriette Kress.