The evidence for the continuing accretion of gas by the Milky Way involves high-velocity clouds, or HVCs--mysterious clumps of hydrogen, moving rapidly through the outer regions of the galaxy.
There are over 50 studies proving this evidence.
( z1 prove :ARG0 ( z2 study :quant ( z3 over :op 50 ) ) :ARG1 ( z4 thing :ARG0-of ( z5 evidence ) :mod ( z6 this ) ) )