TY - CONF AU - Tara Fortier AU - Neil Ashby AU - James Bergquist AU - M Delaney AU - Scott Diddams AU - Thomas Heavner AU - Leo Hollberg AU - Wayne Itano AU - Steven Jefferts AU - K Kim AU - Filippo Levi AU - Luca Lorini AU - W Oskay AU - Thomas Parker AU - Jon Shirley AU - J Stalnaker C2 - IEEE International Frequency Control Symposium Jointly with the 21st European Frequency and Time Forum , Geneva, SZ DA - 2007-01-01 LA - en PB - IEEE International Frequency Control Symposium Jointly with the 21st European Frequency and Time Forum , Geneva, SZ PY - 2007 TI - Improved Limits on Variation of the Fine Structure Constant and Violation of Local Position Invariance ER -