  We consider the two-loop massless propagator-type Feynman diagram with an
arbitrary (non-integer) index on the central line. We analytically prove the
equality of the two well-known results existing in the literature which express
this diagram in terms of ${}_3F_2$-hypergeometric functions of argument $-1$
and $1$, respectively. We also derive new representations for this diagram
which may be of importance in practical calculations.
