Ronkainen, H., K. Holmberg, A. Laukkanen, T. Andersson, M. Kano, T. Horiuchi, and T. Suzuki. “The Effect of Coating Properties on the Performance of a-C:H and Ta-C Films”. Tribologia - Finnish Journal of Tribology, vol. 31, no. 3-4, Mar. 2012, pp. 3-10, https://journal.fi/tribologia/article/view/69336.