Bulgarian stamps for Spring

These beautiful, colorful postage stamps from Bulgaria were designed by the prolific graphic artist, Stefan Kanchev. The set of 6 stamps welcome the arrival springtime in 1971 with stylized birds, flowers, and rays of sunshine.
vintage postage stamp with birds designed by Stefan Kanchev
vintage Bulgarian postage stamp art for Spring 1971, green 2

retro Bulgarian postage stamp art for Spring 1971, blue 5

I notice when overlaying the different patterns, the symmetry connecting the series is accentuated.
symmetry in Stefan Kanchev postage stamp pattern designs
Stefan Kanchev's graphics for this series remind me a little of Alexander Girard's "Tree of Life" and his work for the restaurant La Fonda del Sol.