My PhD examiners have asked me to refer to equations using Eq. (6) rather than Eq. 6. This seems simple enough, but often I have sentences of the form:

"This is a fact related to an equation you passed many pages ago (see Eq. 6)."

To me it seems insane to rewrite this as:

"This is a fact related to an equation you passed many pages ago (see Eq. (6))."

What are the accepted ways of formatting the equation number in parenthetical references?

  • 1
    What is your scientific field? If you want to know the accepted ways of referencing equations I suggest you'd read other papers in your field. That being said, I think it would be wise to follow your examiners' advice.
    – Boondoggle
    Commented Sep 1, 2018 at 22:55
  • 1
    You could sidestep it by making the comment non-parenthetical, e.g. "ago, viz. Eq. (6)".
    – J.G.
    Commented Sep 2, 2018 at 6:12
  • both good ideas, if no better ideas are suggested I'll do the second; in answer to the first my thesis is very interdisciplinary- it goes from abstract algebra to immunology; this examiner is an engineer.
    – Abijah
    Commented Sep 3, 2018 at 14:47

2 Answers 2


Another approach is to use commas to set off the back reference rather than parenthesis:

"This is a fact related to an equation you passed many pages ago, Eq. (6)."


Section 12.24 of The Chicago Manual of Style suggests that equations should be centered on the line and the number label enclosed in parenthesis. When referencing that equation in text, you simply refer to it using the same label, also enclosed in parenthesis. In your example, you might write this instead:

"This is a fact related to equation (6) you passed many pages ago."

If you are writing this in LaTeX, you may find that such typesetting is done automatically. See LaTeX: Cross referencing for a comprehensive guide on preferred usage.

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