  Single-particle kinetic energy spectra and two-particle small angle
correlations of protons ($p$), deuterons ($d$) and tritons ($t$) have been
measured simultaneously in 61A MeV $^{36}$Ar + $^{27}$Al, $^{112}$Sn and
$^{124}$Sn collisions. Characteristics of the emission sources have been
derived from a ``source identification plot'' ($\beta_{source}$--$E_{CM}$
plot), constructed from the single-particle invariant spectra, and compared to
the complementary results from two-particle correlation functions. Furthermore,
the source identification plot has been used to determine the conditions when
the coalescence mechanism can be applied for composite particles. In our data,
this is the case only for the Ar + Al reaction, where $p$, $d$ and $t$ are
found to originate from a common source of emission (from the overlap region
between target and projectile). In this case, the coalescence model parameter,
$\tilde{p}_0$ -- the radius of the complex particle emission source in momentum
space, has been analyzed.
