I like to have link of free e books on digital signal processing and fourier series, transform.

 

I'm amazed that you haven't already found Steve Smith's ebook on Digital Signal Processing. You can't swing a dead Google cat without hitting it.

http://www.dspguide.com/

 

I like to have link of free e books on digital signal processing and fourier series, transform.

Further to Papabravo's suggestion of Steve Smiths e-book which I fully endorse, can I suggest that you also look through our Useful Websites thread at the head of the Electronic Resources forum for further resources that may be of help to you.

Dave