chore: add reference for abbreviation IRI (#70)

Author: juliapampus

negotiation/contract.negotiation.protocol.md

@@ -14,7 +14,7 @@ This document outlines the key elements of the contract negotiation protocol. Th
 ## Contract Negotiation Protocol
 
 A contract negotiation (CN) involves two parties, a _provider_ that offers one or more assets under a usage contract and _consumer_ that requests assets.
-A CN is uniquly identified through an IRI. Each CN requires a newly generated IRI, which may not be used in a CN after a terminal state has been reached.
+A CN is uniquely identified through an [IRI](https://www.w3.org/International/articles/idn-and-iri/). Each CN requires a newly generated IRI, which may not be used in a CN after a terminal state has been reached.
 A CN progresses through a series of states, which are tracked by the provider and consumer using messages. A CN transitions to a state in response to an acknowledged message from
 the counter-party. Both parties have the same state of the CN. In case the states differ, the CN is terminated and a new CN has to be initiated.