and are more time consuming to process. 3,8 On the other hand, also the
costs of different ILL requests vary significantly, with a huge
difference between straightforward requests and the most
difficult ones. Hence, allocating the same amount of costs to
these different types of requests would be inaccurate. 3 Third,
contrary to overall library costs, specific ILL costs have been
extensively studied in the past, frequently as one of the four
general agreed ILL evaluation criteria: fill rate, turnaround time,
user satisfaction and cost. 9 In the following paragraphs, we
summarize the findings of some relevant studies. For a more
extensive overview of ILL cost studies, we refer to Stein.