¹Due to limitations to length and scope of the paper, a full, theoretical background of the PA problem is not discussed here. A full discussion in the context of this study is given in the full thesis, and especially in Meier, Eide (2007), IEA (2007), and Murtishaw, Sathaye (2006). Contact the author directly for a copy of the original thesis, or visit this link on ResearchGate.com: DOI:10.13140/2.1.3457.6967