↑NIST. “Unit of luminous intensity(candela)”. 《The NIST Reference on Constants, Units, and Uncertainty》. 2016년 3월 1일에 확인함. The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.