This paper studies the optimal contract offered by an uninformed principal to an informed agent when standard assumptions on the shape of the reservation utility profile don't hold. I first exhibit conditions for the continuity and the uniqueness of the solution. I then characterize the solution...

A seller sells a good of unknown quality to a buyer. He may certify his product , that is, announce that quality is at least equal to a certification level. If he doesn't observe himself the quality, he must first investigate to discover the quality before taking his certification decision. The...