The ASSR was first described over 30 years ago, and independently investigated by groups of researchers in Melbourne Australia and Toronto Canada. In clinical audiology, the common application of ASSR is estimation of auditory thresholds in children with severe to profound hearing loss. Due to unavoidable constraints in the maximum effective intensity level of transient (very brief) stimuli used to evoke the ABR, we needed a technique for proper definition of the degree of hearing loss in this population.
There are many articles on the ASSR, and also a book devoted to the topic (edited by Australian audiologist Gary Rance). I include a discussion of ASSR in several PPT presentations available on this web site. One brief PPT presentation devoted to the topic is available here. You'll also find a very thorough review of ASSR by Dr. De Wet Swanepoel in our book Objective Assessment of Hearing.