@InProceedings{Lenzen2009tight,
	author=	{Christoph Lenzen and Thomas Locher and Roger Wattenhofer},
	title=	{{Tight Bounds for Clock Synchronization}},
	booktitle=	{{28th ACM Symposium on Principles of Distributed Computing (PODC), Calgary, Canada}},
	month=	{August},
	year=	{2009},
}