Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. Brainard et al. https://www.jneurosci.org/content/jneuro/21/16/6405.full.pdf
Phototransduction by retinal ganglion cells that set the circadian clock. Berson et al. https://science.sciencemag.org/content/sci/295/5557/1070.ful...