This is not an article about DNP-NMR spectroscopy, however, it deals with the measurements of temperatures in solid-state NMR experiments using KBR and referencing its chemical shift to 13C of adamantane in unstable magnetic fields.
Purusottam, R.N., G. Bodenhausen, and P. Tekely, Determination of sample temperature in unstable static fields by combining solid-state (79)Br and (13)C NMR. J Magn Reson, 2014. 246(0): p. 69-71.
http://www.ncbi.nlm.nih.gov/pubmed/25072191
Monitoring the isotropic chemical shifts to calibrate the sample temperature presupposes a perfect stability of the static magnetic field. It can be difficult to satisfy this requirement in solid-state NMR measurements. This paper describes a simple way to recover the accurate temperature dependence of the (79)Br resonance after subtracting changes of resonance frequency due to variations of the static field, monitored by the (13)C resonance.