This book uses a simplified long-channel EKV model (Slide 0140) which is square-law above threshold, but unlike the ordinary square-law model, includes a long-channel subthreshold model. Channel-length modulation is tacked on using the lambda = 1/(V*L) approach (0124) in saturation. I did not find an expression for gds in subthreshold that includes short-channel effects. The entire design philosophy is to stay above subthreshold and below velocity saturation. Slide 0152 indicates this approach became obsolete in 2004! Nonetheless, the book is no more out of date than most, and has a lot of useful information and guidance.