'Peer review' refers to a procedure whereby a journal, conference or book publisher invites experts in the field to make an evaluation of the scientific merits and fitness for publication of manuscripts offered for publication. The peer review should focus on the entire manuscript to be published, not just on the abstract. The peer review may take the form of a double or single blind, or the identities of both the reviewers and the authors may be openly known to the parties. A book publisher can meet the Level 1 criteria if it has a credible quality assessment by the editors of the work.