Daniel Valencia C. did the following in 2017:
\citep[\textit{apud} \citep{Key2}]{Key1}
There is a better way to do apud than this one?
This blog post by Juliana Fajardini from 2013 mentions an \apud command:
\apud{autor_indireto}{autor_direto}
But I could not reproduce it on Overleaf. It gives me an error for command not recognized.
abntex2citepackage to do citations in the ABNT format. The\apudmacro comes from this package, that's why it won't work unless you\usepackage{abntex2cite}. Nowadays though it's probably better to use\usepackage[backend = biber, style = abnt]{biblatex}for citations in the ABNT style. – Daniel Diniz Jan 30 '24 at 20:42