sentences:  (−2,3,7) pretzel knot
  
  In geometric topology, a branch of mathematics, the (−2, 3, 7) pretzel knot, sometimes called the Fintushel–Stern knot (after Ron Fintushel and Ronald J. Stern), is an important example of a pretzel knot which exhibits various interesting phenomena under three-dimensional and four-dimensional surgery constructions.The (−2, 3, 7) pretzel knot has 7 "exceptional" slopes, Dehn surgery slopes which give non-hyperbolic 3-manifolds.