Supress warning with duplicate citation

_config.yml

@@ -33,7 +33,7 @@ sphinx:
     html_last_updated_fmt: "%b %d, %Y"
     bibtex_bibfiles: ["docs/refs.bib"]
     nb_execution_show_tb: True
-    suppress_warnings: ["mystnb.unknown_mime_type"]
+    suppress_warnings: ["mystnb.unknown_mime_type", "bibtex.duplicate_citation"]
     nb_custom_formats:  # https://jupyterbook.org/en/stable/file-types/jupytext.html#file-types-custom
         .py:
             - jupytext.reads