Oes mergers and acquitions create value?

This is a dissertation For a Msc degree in Finance.The title as specified is about mergers and if they create value. In the dissertation you must include an analysis which will include descriptive statistics. AS you will see in the literature , in order to do that you must find the cumulative average abnormal returns, returns in the stock and compare them. I will include some set of data but you have to choose around 40 companies which have merged to carry on.
Also i will upload some usefull articles that i have found.