Explicitly set citation numbers for some references in natbib

Question

I am writing a review paper that discusses a set of core references and additionally cites other supporting references. Since I want to add citation numbers to plots created outside of latex and because the core references are more important, I want to explicitly set their numbers such that they have the smallest numbers starting with 1.

I am looking for a solution similar to the one in the accepted answer in this related thread: How to customize bibtex numbering in a document? that works with natbib and does not require manually entering bibliography items.

Other related thread: How to fix citation number [IEEE style] for some references

Additional information: I use \usepackage[numbers, square]{natbib} and \bibliographystyle{unsrtnat} and work in overleaf.

Answer 1

I just found my own quick and dirty workaround: Add sort&compress keyword to natbib \usepackage[numbers, square, sort&compress]{natbib} to force references to be numbered in the order of appearance in the text. Then, cite target references at the beginning of the document invisibly, e.g. by using \phantom{\cite{<refkey1>,<refkey2>,...}}. This will result in the target references appearing first in the bibliography.