In-text citations are numbered in Vancouver style, using either parentheses, square brackets, or superscript numbers. Be consistent with the style you use throughout your paper. Number your citations based on the order they appear. Your reference list will keep this same order. If you cite the same source more than once, it will keep the same number each time it is used. If you cite more than one reference in the same sentence, place a common between the two numbers.
Examples
...as evidenced by an influential study on this topic.(1)
...as evidenced by an influential study on this topic.[1]
...as evidenced by an influential study on this topic.1
Several other studies confirmed these findings.(2,3)
Several other studies confirmed these findings.[2,3]
Several other studies confirmed these findings.2,3