Convex Hulls of Finite Sets of Poin ts in Two and Three Dimensions
The convex hulls of sets of n poin ts in two
and three dimensions can be determined with O(n 
log n) operations.  The presented algorithms use the "divide
and conquer" technique and recursively apply 
a merge procedure for two nonin tersecting convex hulls.
 Since any convex hull algorithm requires at 
least O(n log n) operations, the time complexity of the
proposed algorithms is optimal within a multiplicative 
constant.
CACM February, 1977
Preparata, F. P.
Hong, S. J.
