http://www.le.ac.uk/users/rjm1/cotter/
http://www.sis.pitt.edu/~ir/KS/Data/RMiles/contents.html
http://www.eskimo.com/~scs/cclass/notes/top.html
http://www.tti.unipa.it/~ricrizzo/KS/Data/PBurden/chap1.Exercises.html
http://legoexternal.23video.com/v.ihtml?source=share&photo%5fid=7621683
spatialreference.org - 7330,7331
questions: http://www.cprogramming.com/tutorial.html