All examples in this Bongard Problem are outlines of shapes.
M. M. Bongard, Pattern Recognition, Spartan Books, 1970, p. 219.
Adjacent-numbered pages: BP12 BP13 BP14 BP15 BP16  *  BP18 BP19 BP20 BP21 BP22
finished, traditional, bongard
shape_outline [smaller | same | bigger]
Mikhail M. Bongard