Gleixner, G., & Schmidt, H.-L. (1998). On-line determination of group-specific
isotope ratios in model compounds and aquatic humic substances by coupling pyrolysis to GC-C-IRMS. In B. A., Stankiewicz,
& P. F., Van Bergen (Eds.), Nitrogen-containing macromolecules
in the bio- and geosphere (pp. 34-46). American Chemical Society.