2009VDI/VDE/DGQ 2618 Blatt 4.4-2009 Inspection of measuring and test equipment - Test instruction for reference gauges with plane-parallel or spherical measuring faces and for spherical-end gauges and internal callipers
2006VDI/VDE/DGQ 2618 Blatt 4.4-2006 Inspection of measuring and test equipment - Test instruction for setting standards for micrometers