Let 
be the knot above, and let the homomorphism 
taking a knot 
to its companion knot 
be faithful (i.e., taking the preferred
longitude and meridian of the original torus to the referred longitude and latitude
of the tubular neighborhood). Then 
is an untwisted doubled knot of 
. Otherwise, 
is a doubled knot with 
twists (Rolfsen 1976, p. 112).
