ISO 80000-10:2009 10-27.a
ISO 80000-10:2009 10-33.a
ISO 80000-10:2009 10-82.a
ISO 80000-12:2009 12-33.a
ISO 80000-13:2008 13-12.a
ISO 80000-13:2008 13-14.a
ISO 80000-14:2008 14-5.8.a
ISO 80000-14:2008 14-7.17.a
ISO 80000-3:2006 3-12.a
ISO 80000-3:2006 3-13.a
ISO 80000-3:2006 3-7.a
ISO 80000-8:2007 8-1.a
ISO 80000-8:2007 8-29.a
The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the groundstate of the caesium-133 atom
