1. Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281.
2. Cashman, K. D., Dowling, K. G., Škrabáková, Z., Gonzalez-Gross, M., Valtueña, J., De Henauw, S., ... & D-a-j-a (76524). (2016). Vitamin D deficiency in Europe: pandemic? The American journal of clinical nutrition, 103(4), 1033-1044.