Ikeda, S. et al.: Hyoujun Hihukagaku (in Japanese), Igakusyoin (2001), 4-14
Oikarinen, A. : Aging of the Skin Connective Tissue: how to Measure the Biochemical and Mechanical Properties of Aging Dermis, Photodermatol Photoimmunol Photomed. Apr; 10(2) (1994), 47-52.