In Section II-C, we introduced studies that explicitly discussed reasons for patch rejection. In this section, we further report studies that have addressed the general quality issue of software patches and artifacts. Fry et al. conducted a human study, in which participants performed tasks to demonstrate their understanding of the functionality and maintainability aspects of software patches [28]. Bettenburg et al. empirically investigated the quality of bug reports from the perspectives of both developers and end-users [8]. Hooimeijer and Weimer proposed a descriptive model of bug report quality, which was used to filter uninformative incoming bug reports or suggest missing features from bug reports [29].