@InProceedings{Sommer2009Gradient,
	 author =	{Philipp Sommer and Roger Wattenhofer},
	 title =	{{Gradient Clock Synchronization in Wireless Sensor Networks}},
	 booktitle =	{{8th ACM/IEEE International Conference on Information Processing in Sensor Networks (IPSN), San Francisco, USA}},
	 month =	{April},
	 year =		{2009}
}