Although I have found similar questions on this site they were not what I was looking for.
I have modified the source code of an MIT licensed project, and I have added new classes to it as well. Please correct me if I am wrong, but I think that it is legal to add my copyright notice above the license and remove the other one. But how should I attribute the contribution of the previous authors? Should I use a separate file? There are also some html files with no license or copyright notice in them which I also modified. Do I have to handle them differently?
My question is different than this question in that I have also modified some of the files of the project I am extending.