I thought this might be of interest to the researchers:
I was just reading an article from http://www.thujone.info discussing the chemical in absinthe.
What struck me was this text, the sixth paragraph in the “definition of pre-ban absinthe” section:
“Typical historic recipes are given in the books of Duplais , Fritsch , Bedel  and de Brevans . The composition of herbs used along with the wormwood differs from recipe to recipe. To improve the taste or add coloring, anise, star anise, lemon balm, hyssop, juniper, nutmeg, veronica, angelica root, melissa, coriander, camomile or parsley were added. Each country produced its own types of absinthe. For example, in the Czech Republic, peppermint was added, but neither anise nor fennel. In Switzerland, melissa, hyssop or angelica root were added to the Swiss alpine wormwood, which was a valued ingredient due to its strong aroma , while in France, coriander was added.”
Note the source numbers. I checked the references section at the end of the PDF, and numbers 27, 28, 30, and 31 correspond respectively with publications from the years 1891, 1908, 1882, and 1899. I certainly would like to see these sources, but their dates can be safely assumed to be authentic. And why not?
So what am I getting at with all this research? This quote:
“For example, in the Czech Republic, peppermint was added, but neither anise nor fennel.”
It must come from one of those antique source materials.