Generally, the References Only view displays your references without PMID or DOI links. In some cases, however, DOIs are an integral part of your references and are displayed in the References Only view. 

APA Style

If you selected APA5 or APA6 as the editorial style for your reference job, DOIs are included in the References Only view because the APA editorial style recommends including DOIs in all references, when available. APA 6th edition, in particular, heavily emphasizes the inclusion of DOIs in references as the best way to identify an online source.

No First Page

If a reference in any editorial style does not include a first page but does link to Crossref, a DOI is included in the reference in the References Only view. We have found that most print publishers will include the DOI in a reference if there is no page range available, even if they otherwise would not do so, and we have adopted this solution across all of our editorial styles in order to make referenced sources more identifiable and easier to find.