1. By superscript numbers, which appear outside the punctuation if the citation applies to a whole sentence or clause.
Roasted pumpkin seed oil was found to contain higher levels of α- and γ-tocopherol than roasted sunflower oil. 13
2. By italic numbers, in parentheses on the line of text and inside the punctuation.
At the end of the process, caffeine content is usually reduced to 0.02−0.3% (13).
1. St-Gelais, A. T.; Aeppli, C.; Burnell, C. A.; Costa-Pierce, B. A. Non-dioxin like polychlorinated biphenyl indicator congeners in Northwest Atlantic spiny dogfish (Squalus acanthias). Mar. Pollut. Bull. 2017, 120 (1-2), 414-421. DOI:10.1016/j.marpolbul.2017.05.001
2. Morgan, A. C.; Sulikowski, J. A. The role of spiny dogfish in the northeast United States continental shelf ecosystem: How it has changed over time and potential interspecific competition for resources. Fish. Res. 2015, 167 (7), 260-277. DOI:10.1016/j.fishres.2015.03.004
3. Lee, E.; Lee, S. K.; Kim, M. J.; Lee, S. Simple and rapid detection of bisphenol A using a gold nanoparticle-based colorimetric aptasensor. Food Chem. 2019, 287, 205-213. DOI:10.1016/j.foodchem.2019.02.079
4. Sargent, W. Crab wars : a tale of horseshoe crabs, bioterrorism, and human health; University Press of New England: Hanover, 2002.
5. Grant, C. S.; Louda, J. W. Scytonemin-imine, a mahogany-colored UV/Vis sunscreen of cyanobacteria exposed to intense solar radiation. Org. Geochem. 2013, 65 (12), 29-36. DOI:10.1016/j.orggeochem.2013.09.014