oscillator / crystal
Oscillator
http://whatis.techtarget.com/definition/0,,sid9_gci212723,00.html
Crystal and Frequency Control Glossary
http://www.icmfg.com/crystalglossaryo.html
Fundamentals of Quartz Oscillators
http://cp.literature.agilent.com/litweb/pdf/5965-7662E.pdf