# how to cite an equation that is common knowledge but I use others notation

I am writing my masters thesis on an econometrics topic. It is very closely related to another paper by NW. Since our papers are very closely related, I am using their notation in order to draw comparisons (which I state before introducing my model).

NW motivate their model using known findings from their field. They demonstrate that the standard model does not behave well under their assumptions by (mathematically) decomposing the standard model's objective function. This approach is very common, however, every author formats their arguments to fit their purpose. In my paper, I want to build on NWs argument. I.e. I want to make the same point and extend it. Do I need to cite their equation (the decomposition of the objective function) in any special way?

To paraphrase what I currently have:

... NW illustrate this by deconstructing the expectation of the objective function into a signal term and a noise term

$$E[Q(\beta)] = Eg(\beta)'Wg(\beta) + tr(W Omega(\beta))$$

...

(I copy their notation exactly.)

The reason I am unsure is that NWs argumentation is not unique to their paper but how they frame it is.