Articles in many online-only journals have no volume or page numbers. In this case, follow the journal title with the DOI:
Hirsh Å, Nilholm C, Roman H, Forsberg E & Sundberg D (2020). Reviews of teaching methods – which fundamental issues are identified? Education Inquiry, doi:10.1080/20004508.2020.1839232.
Some journals use document numbers, sometimes preceded by a letter. Place this number after the volume (or volume and issue) number; use the notation used by the journal:
Smale DA & Wernberg T (2013). Extreme climatic event drives range contraction of a habitat-forming species. Proceedings of the Royal Society B: Biological Sciences 280:20122829, doi:10.1098/rspb.2012.2829.
Daskin JH, Bell SC, Schwarzkopf L & Alford RA (2014). Cool temperatures reduce antifungal activity of symbiotic bacteria of threatened amphibians – implications for disease management and patterns of decline. PLoS ONE 9(6):e100378, doi:10.1371/journal.pone.0100378.
Ridgway KR (2007). Long-term trend and decadal variability of the southward penetration of the East Australian Current. Geophysical Research Letters 34:L13613, doi:10.1029/2007GL030393.
If no DOI is provided, include the direct URL for the article: