The International Code of Botanical Nomenclature St. Louis code defines a valid publication as:

• Article 29.1. Publication is effected, under this Code, only by distribution of printed matter (through sale, exchange, or gift) to the general public or at least to botanical institutions with libraries accessible to botanists generally. It is not effected by communication of new names at a public meeting, by the placing of names in collections or gardens open to the public, by the issue of microfilm made from manuscripts, typescripts or other unpublished material, by publication online, or by dissemination of distributable electronic media.