I want to find some very respectable research that unveils the importance and efficiency of calls to action.
Here is a great article on how to create unbeatable Call to actions:
I think the basics to remember are make the wording concise yet compelling, and make the button attractive and obvious.
Hope this helps,
I think you can use the Eyetracking Web Usability by Nielse as a starting point to your research. Basically call to action buttons tend to have one of the following properties:
This is made on purpose so that once you enter the page and your eyes start scanning the page, that button will be the first thing you notice. Sorry I can not point you to a specific research paper. Just be careful when you reach to conclusions after reading some blog posts, articles... I've seen some interesting discussions around the web that just changing one button to one color increased the clicks by X%. Keep in mind that all this depends on the context and lots of external variables.