“…Furthermore, as mentioned in Section 1, since DLs are destined to serve user communities, the user’s opinion is one of the main aspects to be considered in the quality evaluation of DLs. For these reasons, techniques that require the user’s participation such as interviews and questionnaires are the focus of this review, and the prime methods for collecting qualitative data [8, 18, 25, 31–33, 35, 36, 38–47, 49–53]. In addition, observations in which user actions are recorded are also common methods for obtaining data [23, 24, 28, 63].…”