I found this paper from 1987 https://sci-hub.se/https://doi.org/10.1111/j.1751-1097.1987.tb04757.x https://sci-hub.se/https://doi.org/10.1111/j.1751-1097.1987..

I found this paper from 1987 https://sci-hub.se/https://doi.org/10.1111/j.1751-1097.1987.tb04757.x https://sci-hub.se/https://doi.org/10.1111/j.1751-1097.1987.... You will also find lots of experience reports and discussions of appropriate light sources on numerous grower sites.