In-text citations are numbers in square brackets. References are numbered in the order in which they are cited. If you are citing more than one source in the same phrase or sentence, use a separate bracket for each number with a comma between them. If you are citing three or more references in sequence, include the the first and last numbers in square brackets with a dash between them.
Example: as shown by Brown [4], [5]; as mentioned earlier [2], [4]–[7], [9]; Smith [4] and Brown and Jones [5]; Wood et al. [7]
In-text citations can also be treated as nouns. Instead of using the author name, refer to the source by number.
Example: as demonstrated in [3]; according to [4] and [6]–[9].