In our study of periodic orbits we will work with oriented knots and links. To each crossing C in an oriented knot or link we associate a sign as shown in Figure 5.10.
Figure 5.10: Crossing conventions: (a) positive (b) negative.
A positive cross (also known as
right-hand cross, or overcross)
is written as 
. A
negative cross
(also known as a left-hand cross, or undercross) is written
as . This definition of crossing is
the opposite of the
Artin crossing convention adopted by Solari and Gilmore [4].