If you're looking for literature on the topic, probably the best bet is to search a database called EconLit. If you're looking for data, in the Preqin database you can specify in an Investor search that you are interested in Private Equity investors and limit your 'Investor Type' to 'Sovereign Wealth Fund'. (There are further filters you can apply, if you'd like to make your search more specific.) Details on each fund are generally limited, but they usually include a portfolio breakdown, brief background information and sometimes annual report documents.