The contents of the courses here are based on the books "GATEway to Chemical Engineering (set of 5 volumes)" by

M Subbu, D K Sandilya, K Nagarajan, S Siddarth, and R Pavan 

"An Insight into Chemical Engineering" by M Subbu

(Rishal Publications, Chennai, India)

The questions are predominantly from GATE-CH 1988-2021, and typical questions from other relevant streams of GATE, and other sources.