Begley P, Foulger B, Simmonds P. Femtogram detection of perfluorocarbon tracers using capillary gas chromatography-electron-capture negative ion chemical ionisation mass spectrometry. J. Chromatogr. 1988, 445 (1): 119–128. PMID 3215967. doi:10.1016/s0021-9673(01)84513-1.
Begley P, Foulger B, Simmonds P. Femtogram detection of perfluorocarbon tracers using capillary gas chromatography-electron-capture negative ion chemical ionisation mass spectrometry. J. Chromatogr. 1988, 445 (1): 119–128. PMID 3215967. doi:10.1016/s0021-9673(01)84513-1.