(EN) ISO/TS 19408:2015(en), su iso.org, 2015. URL consultato il 17 febbraio 2016.
«maximum horizontal distance from the centre of the back of the heel (maximum point of heel curve) to the end of the most prominent toe, with the subject standing with the weight of the body equally distributed on both feet, barefoot or wearing thin hose that does not significantly affect the dimensions of the foot»
