NIST Physics Laboratory
Two-way Satellite Time Transfer
GPS Time Transfer
UK National Physical Laboratory
JPL Frequency Standards Laboratory
GALILEO - European Satellite Navigation System
esa - News On Navigation
UFFC - Atomic Clocks - Past, Present, and Future
Abenteuer Universum
metas - Labor für Zeit und Frequenz
Physikalisch-Technische Bundesanstalt - Wissenswertes zur Zeit