Use the Forms 5500 Series Search on EFAST, U.S. Department of Labor.

Go to FreeERISA to search Forms 5500. This is a free resource, but registration is required. 

Go to PIonline.com — Pensions & Investments.

For articles, search for the journal Pensions & Investments, available through ABI/INFORM Global (look under Publication) and in Business Source Complete (choose Advanced Search).