The studies of Stank, Keller & Daugherty (2001) and Gimenez & Ventura (2003 and
2003b) share a common aim: to analyse the impact of internal and external integration
on performance. The integration-performance models of these authors included also a
relationship between the levels of internal and external integration. All of them found
that these levels of integration are positively correlated. This suggests that they
positively influence each other.