Principles and solid background on PO formalism are found in several and highly recommended articles ( 86JMR433-68 , 88ANG490 , B90GRA51 , 90ANG383 , 00ENC1875 )

Implementation in Mathematica:

( 91JMR612-94 )

POMA ( 93JMRA103-101 )

Cartesian PO

C3PO method ( 94JMRA14-107 )