If you want to refer to a previous reference, do not provide a new citation number, nor use ‘ibid.’ (meaning ‘the same’) or ‘op. cit.’ (meaning ‘the work cited’) terms. If you want to refer to the same source twice or multiple times, simply repeat the earlier citation number and then use that same number in all subsequent citations throughout the body of the paper.
The separate instances of referring to the same source should be made in text, for example, when referring to another fact, idea or an opinion found within the same source at different page numbers, use the following forms: [2, pp. 3-5], [5, eq. (2)] for referring to an equation, [5, Sec. IV] a section, [5, Tab. 3] a table, [1, Ch. 2] a chapter, etc.