also relevant: https://www.researchgate.net/publication/354376762_THE_INFLUENCE_OF_VITAMIN_D_ON_COVID-19_OUTCOMES_Chapter_4_of_Covid-19_and_Nutraceuticals_A_Gui

also relevant: https://www.researchgate.net/publication/354376762_THE_INFLUENCE_OF_VITAMIN_D_ON_COVID-19_OUTCOMES_Chapter_4_of_Covid-19_and_Nutraceuticals_A_Guidebook_Bohr_Publishers_and_New_Century_Health_Publishers_LLC https://www.researchgate.net/publication/354376762_THE_INFLU...