Handa, I.T., Korner, C. and Hattenschwiler, S.  2005.  A test of the treeline carbon limitation hypothesis by in situ CO2 enrichment and defoliation.  Ecology 86: 1288-1300.

Hattenschwiler, S., Handa, I.T., Egli, L., Asshoff, R., Ammann, W. and Korner, C. 2002. Atmospheric CO2 enrichment of alpine treeline conifers. New Phytologist 156: 363-375.

Streit, K., Siegwolf, R.T.W., Hagedorn, F., Schaub, M. and Buchmann, N. 2014. Lack of photosynthetic or stomatal regulation after 9 years of elevated [CO2] and 4 years of soil warming in two conifer species at the alpine treeline. Plant, Cell and Environment 37: 315-326.