How to eliminate the indent in reference

I’m using IEEE as my referencing style.
Here is the document class of my article

documentclass[conference]{IEEEtran}

Then I applied

bibliographystyle{IEEEtran}
bibliography{IEEEabrv,ref}

But I got the reference list like this:

I guess this was caused by the indent of the reference section. Can anyone tell me how to address this issue? Probably adding indents to all the reference lines.

Thanks!!