Photoperiod Control Systems for Greenhouse Crops, Boyle, T., University of Massachusetts Amherst Extension, 2017
Greenhouse Lighting, Neil S. Mattson, Cornell University Extension, 2014. http://www.greenhouse.cornell.edu/structures/factsheets/Greenhouse%20Lighting.pdf
Managing Photoperiod in the Greenhouse, Christoper J. Currey, Roberto G. Lopez and Erik S. Runkle, Purdue University Extension, 2013.
https://ag.umass.edu/greenhouse-floriculture/fact-sheets/photoperiod-control-systems-for-greenhouse-crops
Measuring Daily Light Integral in a Greenhouse, Arianna P. Torres and Roberto G. Lopez, Purdue University Extension. https://farm-energy.extension.org/wp-content/uploads/2019/04/1.-E-3160.pdf
Greenhouse Energy Conservation Strategies, Erik Runkle, Michigan State University Extension, and A.J. Both, Rutgers New Jersey Agricultural Experiment Station, 2011.
https://farm-energy.extension.org/wp-content/uploads/2019/04/1.-E-3160.pdf
Considering Supplemental Lighting?, A.J. Both, Rutgers University New Jersey Agricultural Experiment Station, 2008. https://nj-vegetable-crops-online-resources.rutgers.edu/wp-content/uploads/2015/06/Greenhouse-Supplemental-Lighting.pdf
Evaluating Supplemental Light for Your Greenhouse, Paul Fisher, Caroline Donnelly and James Faust, University of New Hampshire Cooperative Extension, 2001.
http://www.greenhouse.cornell.edu/crops/factsheets/SuppLight.pdf