V. T. Ponkilainen, T. T. Huttunen, M. H. Neva, L. Pekkanen, J. P. Repo, and V. M. Mattila, “National trends in lumbar spine decompression and fusion surgery in Finland, 1997–2018”, ActaO, vol. 92, no. 2, pp. 199–203, Oct. 2020.