Dating back to 1892/3, the HCCH became a permanent intergovernmental organization in 1951. Its role is to facilitate the increasing unification of the rules of private international law." The Statute (link below) sets out structure and purpose.
The HCCH's own website makes available the full text and status details of the various Conventions it has developed.
Hague Conference on Private International Law can be used as subject search in SOLO
Monographs with shelf marks beginning Private Int are on Level 3.
The Elgar Companion to the Hague Conference on Private International Law by 
Civil Jurisdiction and Judgements in EuropeThe Brussels I Regulation, the Lugano Convention, and the Hague Choice of Court Convention by