Finding the courage to write about cowardice

"Coward. Chicken. Yellow-belly." Those were insults the French used against the gunmen who carried out the Charlie Hebdo attacks in January. Cowardice, in fact, is currently enjoying a bit of global resurgence as a put-down. So much so that Boston University professor Chris Walsh decided it was time to write a book about the subject. The first hurdle? Finding source material.