Torn Curtain (1966)
The killing of Gromek strongly resembles Psycho when the peasant wife uses the big knife and stab Gromek.
Mentioned in this behind-the-scenes featurette. A movie poster is also shown.
discussion about how the establishing shots did not look like Leipzig
During the post end credits one of the title cards mentioned that Hitchcock directed six more movies after Psycho.
The character name "Sarah" is a nod to Torn Curtain.
clip shown in trailer