sun-exposure-chart-2

UV Forecast @ Wolfram Alpha

Time to Burn @ Wolfram Alpha

Study: Role of Vitamin D in Cancer Prevention (2006) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1470481/

Sunlight & Vitamin D http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1495109/

Photosynthesis of previtamin D3 in human skin and the physiologic consequences http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1495109/