The “formula” of a
polygonal knot in E3 is defined by appropriate labeling of the crossings
in the regular projection of the knot. Admissible transformations of such
formulas are defined (for example, cancellation of the consecutive symbols x and
x−1), and prime formulas are defined. It is shown that if two knots have
formulas which are equivalent by applications of admissible transformations, and
one of the formulas is prime, then the knots are equivalently embedded in
E3.