You can find the PDF of the notes at https://tinyurl.com/DSPFundamentals
The entire playlist is at • DSP Fundamentals
And some recommended textbooks are:
The Scientists and Engineers Guide to DSP by Smith (https://www.dspguide.com/pdfbook.htm) -- This is a popular book that is freely downloadable.
Discrete-time Signal Processing by Oppenheim & Schafer (https://amzn.to/44G9CH2) -- This is considered a standard reference and follows the same notation that I use in the lectures.
Understanding Digital Signal Processing by Richard Lyons (https://amzn.to/4b7MgO5) -- This presents DSP concepts in a very accessible manner with excellent practical explanations. It is less in-depth than the Oppenheim & Schafer book but easier reading for many.
DSP First by McClellan, Schafer, & Yoder (https://amzn.to/4bSnAta) -- This is a softer introduction to DSP targeted toward college sophomores but in the spirit of the Oppenheim & Schafer book.
(Note, if you purchase any of these books through the links provided, I may receive a small commission through the Amazon Affiliate program. Do not feel obligated.)