Assertion: strip's boundary | /r/HasProperty | simple closed curve
Facets:
Source sentences:
text: Its boundary is a simple closed curve, i.e., topologically a circle.
text: An example of a Möbius strip can be created by taking a paper strip, giving one end a half-twist, and then joining the ends to form a loop; its boundary is a simple closed curve which can be traced by single unknotted string.