Researching treaties is often difficult. Before begining it is helpful to ask some basic questions:
Who are the parties (signatories) to the treaty?
What is the subject of the treaty?
When was the treaty signed? When did it go into effect?
Digest of Unites States Practice in International Law - insights into treaty law from the U.S. Dept. of State
UK Treaties Online - Treaties to which the UK is a signatory