# Seifert conjecture

The conjecture was disproven in 1974 by Paul Schweitzer, who exhibited a ${\displaystyle C^{1}}$ counterexample. Schweitzer's construction was then modified by Jenny Harrison in 1988 to make a ${\displaystyle C^{2+\delta }}$ counterexample for some ${\displaystyle \delta >0}$. The existence of smoother counterexamples remained an open question until 1993 when Krystyna Kuperberg constructed a very different ${\displaystyle C^{\infty }}$ counterexample. Later this construction was shown to have real analytic and piecewise linear versions.