Adams, C. C. The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots.
New York: W. H. Freeman, p. 169, 1994.Bleiler, S. and Scharlemann,
M. "A Projective Plane in with Three Critical Points is Standard. Strongly Invertible
Knots have Property ."
Topology27, 519-540, 1988.Scharlemann, M. and Thompson,
A. "Detecting Unknotted Graphs in 3-Space." J. Diff. Geom.34,
539-560, 1991.
with Three Critical Points is Standard. Strongly Invertible
Knots have Property 
."
Topology 27, 519-540, 1988.Scharlemann, M. and Thompson,
A. "Detecting Unknotted Graphs in 3-Space." J. Diff. Geom. 34,
539-560, 1991.