Merger transaction databases

Hi all,

I am about to begin writing a thesis which analyzes, amongst other things, "merger waves" in the US over the last 20 years.

In order to carry this out I would need an M&A transaction database that could provide me quarterly volumes during this historical time period.

I was wondering if anyone could tell me which databases are best? Do Bloomberg, Datastream, Worldscope, ThomsonOne provide this? I know the best database is the SDC M&A database, but I think I would need to get special authorization for that one.

Thanks in advance