BibTeX, biblatex and biber ⇒ How to add a symbol next to a reference number in reference list and in-text citation using BibTeX

[user_23124]

I am using the Springer Nature latex https://www.springernature.com/de/autho ... or-support for my document with \documentclass[sn-vancouver]{sn-jnl}

How should I modify the BibTex style file (or another approach) to add a symbol next to a single or multiple references as shown in the image below?



Moreover, if a reference number has a symbol next to it in the references list, then the in-text citation should look like the image below:



I would prefer to use BibTex and not have to switch to BibLatex

Thanks.