Academic
A study reported in 1978 at the West Virginia University College of Engineering of the citations found in the master’s theses accepted over a 4-year period (126 theses between 1971-74) showed thatnonjournal (i.e., book) literature was more important in the engineering sciences than previously thought by showing that, of 3,002 references overall, only 1,000 (33.3%) were journal citations, with the proportion of journal citations by department ranging from 11.4% of the references in aerospace theses to 49.4% of the references in chemical theses. (Source)