Based onjustfourcase-studies,anytendencyofover-generalisationshouldbeavoided,butthecasesneverthelessallow
workingoutsomerecurrentpatternsinthecreationandspreadofServPPINs;patternsthatshouldbeseenashypothesesin
need offurthertesting.Thesepatternsareessentiallyoftwokinds. First of all,thereareanumberofobservationsrelatingto
factors ofinfluencethatturnedouttobesimilarinallfourcases.Thesecommonenablingfactorslendthemselvesto
derivingsomeclearlessonsforeachphase.