A two-page note on transition amplitudes. Obviously, a premature
and incomplete pilot of a planned series, with two further sins
committed. First, the idea itself has already been presented and
illustrated earlier, via $V = x^2$. This observation is now
extended, on the level of an easy student's exercise, to $V = x^2
+l(l+1)/x^2$. Second, the bulk of the text basically comprises
just a summary of formulae while their derivation and all the
innovative technical details which could, hopefully, make this
message worth reading are just announced as to be described in an
unspecified future publication [6].

MR2436429 Popov, V. S.; Trusov, M. A. Feynman operator calculus and
singular quantum oscillator. Phys. Lett. A 372 (2008), no. 32,
5274--5275. 81R05 (81S99)