@book {49,
	title = {A practical guide to geostatistical mapping of environmental variables},
	volume = {140},
	number = {4},
	year = {2007},
	isbn = {9279069047},
	author = {Hengl, Tomislav}
}
@book {50,
	title = {Model-based geostatistics},
	year = {2007},
	publisher = {Springer},
	organization = {Springer},
	isbn = {0387485368},
	author = {Diggle, Peter J and Ribeiro, Paulo J}
}
@book {51,
	title = {Geostatistics for environmental scientists},
	year = {2007},
	publisher = {John Wiley \& Sons},
	organization = {John Wiley \& Sons},
	isbn = {0470517263},
	author = {Webster, Richard and Oliver, Margaret A}
}
