A subset 
is said to be bicollared in 
if there exists an embedding ![b:X×[-1,1]->Y](/images/equations/Bicollared/Inline3.svg)
such that 
when 
. The map 
or its image is then said to be the bicollar.
Bicollared
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References
Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, pp. 34-35, 1976.Referenced on Wolfram|Alpha
BicollaredCite this as:
Weisstein, Eric W. "Bicollared." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Bicollared.html