Bergamaschi, P., Brenninkmeijer, C. A. M., Hahn, M., Röckmann, T., Scharffe, D. H., Crutzen, P. J., Elansky, N. F., Belikov, I. B., Trivett, N. B. A., & Worthy, D. E. J. (1998). Isotope analysis based source identification for atmospheric CH4 and CO sampled across Russia using the Trans-Siberian railroad. Journal of Geophysical Research, 103, 8227-8235.