When the Sovietskis designed the MiG-23, rather than do their own math, they copied the swing-wing angles from the F-111.
And when the MiG-23 prototype suffered shock-stall at transonic speeds, instead of doing their homework they just copied the engine inlet ramps from the F-4 Phantom II. Look at the photos side-by-side and the family resemblance is unmistakable.
Neither Russia nor China were shy about imitation technology. Some Hasagawa model kits were also probably used by their respective design bureaus.