jgg     2013 33 (6):  130-132    ISSN: 0412-1961  CN: 21-1139/TG TRANSFORMATION OF VELOCITY FIELD WITHIN NEU COORDINATE  SYSTEM BETWEEN VARIOUS ITRFS Second Monitoring Center, China Earthquake Administration, Xi’an 710054 Received: 2013-07-06  Revised: null  Online: 2013-12-13 Supporting info