What's the "proof" of having presented a project results in a conference? I am a Physics master's student trying for PhD. During my summer internship I worked on a project in a research lab. During the work I found a a few inconsistencies with work done by the Post-Doc and I also redid the analysis with new data. Because of this I was included as second author in a presentation given by the Post-Doc in a conference (our common guide was the third author). I do not have any "proof" as such for this, except for the keynote presentation. How am I supposed to mention this in my CV? I mean, if it was an actual paper I can give a link to the paper, however the conference presentations do not have  any such things I think. Is there any official way to do this or should I just give my guide as a referee so that admission committee will contact the guide in case they need to verify this? 

Because it was presented in a conference I am hoping it'll be published at some point in the future(we are still working on the project), but I have to apply for few institutes with next few months, and the project won't be completed by then.
Most of us have some items on our CVs that have no supporting proof.  I recommend checking what can be found on the internet to be sure the information on your CV matches that information.  If there is a big mismatch between your memory and the written record, you should ask for advice on that. However, if there is no listing at all, go ahead and put down the facts as you know them, before you forget them.

The real issues is whether in your field, people generally list presentations by collaborators.  If not, perhaps it is normal to list on-going projects and collaborations.  Or, if you have a short CV, you can buck convention a bit and list what you think is relevant.  You can remove it later on.

The confirmation of many facts on your CV will come from letters of recommendation.  If your "common guide" writes in a letter it will likely mention the collaboration.  Also, most letter writers will ask for a recent CV, and will tell you if you have anything that looks misleading.

By the way, you probably should not list a URL to any paper you get published.  Stick with the formal bibliographic conventions, and perhaps list at DOI.  If you have something like a code repository, you should then put in a URL.

On more thought.  The fact that your guide can validate this work is just one reason to pick that person as a letter writer (referee).  From what you wrote that seems like a good choice, but you need to think about all sorts of facts. (There are Lots of questions on that sort of thing on this site.)  If you have other letter writers who can expound on your research accomplishments and abilities, you might not select this person as a letter writer.  It still could be fine to list this item on a CV.