I would be happy to send you a pdf scan of the following paper by email.

Chesson, P. 2008. Quantifying and testing species coexistence mechanisms. Pp 119 – 164 in

Valladares, F., Camacho, A., Elosegui, A., Estrada, M., Gracia, C., Senar, J.C., & Gili, J.M., ed.

“Unity in Diversity: Reflections on Ecology after the Legacy of Ramon Margalef.”