  The Trojan Horse nucleus invariance for the binary d(d,p)t reaction was
tested using the quasi free $^2$H($^6$Li, pt)$^4$He and $^2$H($^3$He,pt)H
reactions after $^6$Li and $^3$He break-up, respectively. The astrophysical
S(E)-factor for the d(d,p)t binary process was then extracted in the framework
of the Plane Wave Approximation applied to the two different break-up schemes.
The obtained results are compared with direct data as well as with previous
indirect investigations. The very good agreement confirms the applicability of
the Plane Wave Approximation and suggests the independence of binary indirect
cross section on the chosen Trojan Horse nucleus also for the present case.
