Wang, Y. H., Dumke, R., Zhang, J., Liu, T., Stejskal, A., Zhao, Y. N., Lu, Z. H., Wing, L. J., Becker, T., & Walther, H. (2007). Absolute frequency and isotope shift measurements of the cooling transition in singly ionized indium. European Physical Journal D, 44(2), 307-311. doi:10.1140/epjd/e2007-00171-0.