The information available when researching mergers & acquisitions is highly dependent on the type (private, hostile, etc.) and the stage (pending, completed, terminated) of the deal.
The best databases to begin your M&A research are:
Journals, magazines, and trade publications are great sources for M&A information. To find the database that contains an electronic journal or magazine, use the E-journals tool and search by journal title. Below are a few M&A related journal titles.