Simple				Simple example of a two-way classification table
				where lacking data creates two distinct connected sets
Searle				Example of a two-way classification table where lacking data 
				creates three distinct connected sets. 
				From Searle (1997) 'Linear Models'. Wiley. 324p.
DWD				Example of an unbalanced phenological data set. 
				Phenological observations of nine stations from 1951 to 1998
				from the German Weather Service.
