Peer review is no prerequisite for citation. The first paper I looked at for an example (at the top of today's "Recent" papers in PRD), cites three arXiv entri

Peer review is no prerequisite for citation. The first paper I looked at for an example (at the top of today's "Recent" papers in PRD), cites three arXiv entries, out of 91 references. https://journals.aps.org/prd/references/10.1103/PhysRevD.98.074023 https://journals.aps.org/prd/references/10.1103/PhysRevD.98.... Successful peer review in an upstanding journal is a signal of relative reliability and importance, but it is not the arbiter of usefulness.