  Confusion over different kinds of secondary research, and their divergent
purposes, is undermining the effectiveness and usefulness of secondary studies
in software engineering. This short paper therefore explains the differences
between ad hoc review, case survey, critical review, meta-analysis (aka
systematic literature review), meta-synthesis (aka thematic analysis), rapid
review and scoping review (aka systematic mapping study). These definitions and
associated guidelines help researchers better select and describe their
literature reviews, while helping reviewers select more appropriate evaluation
criteria.
