How can I get the reference of the ring episode in "The Merchant of Venice?"

The following three references trace the ring leit motif found in the second half of the story.

The recourse to an element of three (three caskets, three rings, three confrontations, etc....) are tritely a "fairy tale" element in this already farfetched tale. Shylock the usurer conveniently replaces the ogre and Portia, the fairy godmother!