All examples in this Bongard Problem are oblong outlines of shapes.
M. M. Bongard, Pattern Recognition, Spartan Books, 1970, p. 219.
Adjacent-numbered pages: BP13 BP14 BP15 BP16 BP17  *  BP19 BP20 BP21 BP22 BP23
finished, traditional, bongard
elongated_outline [smaller | same | bigger]
Mikhail M. Bongard