It seems to be authored by Kurt Reiniger. He refers to an aerodynamic "flying V" plus fitting wedge stages as basis
and inspiration for an European mini shuttle on top of EUROPA III.
The ideas seem to be based on the period 1965 to 1969 and his earlier work.
The folder also has an opinion piece by the same K. Reiniger on "NASA Space Shuttle" dated October 1th 1969.
That piece is about 7 different ideas for the Space Shuttle with 1, 1.5 and 2 stages, ballistic to reusable.
It also has a reference to a Bölkow design (February 1965) of a wedge inside a V where
the V is the first stage and the wedge the second stage.
This "V" plus wedge is a type of design that I have not seen before but maybe there is more Bölkow information out there? Anyone?