Precise Time and Time Interval (PTTI) Appl. and Planning Meeting, pp. 687-724, 1981, available online Archived 2011-07-27 at the Wayback Machine.
Precise Time and Time Interval (PTTI) Appl. and Planning Meeting, pp. 687—724, 1981, available online Архивировано 27 июля 2011 года..