The radiocarbon content of samples can be measured by two methods based on different principles:1.	Measuring the 14C radioactivity (the conventional dating method; at Groningen marked with a laboratory code number GrN: Mook & Streurman, 1983; Mook & Waterbolk, 1985), and 2.	Measuring the 14C concentration (by means of AMS, a form of mass spectrometry; at Groningen marked with a laboratory code number GrA: Gottdang et al., 1995; Van der Plicht, 1993).