琥珀 - Wikipedia
Bray, P. S.; Anderson, K. B. (2009). “Identification of Carboniferous (320 Million Years Old) Class Ic Amber”. Science 326 (5949): 132–134. Bibcode :  2009Sci...326..132B . doi : 10.1126/science.1177539 . ^ Electrochemical Supercapacitors for Energy Storage and Delivery: Fundamentals and Application...
ja.wikipedia.org