  Let c be a periodic Reeb orbit on the boundary S of a compact star-shaped
domain C in R4. We show that if there is an immersed symplectic disc f in C
with boundary c then the self-linking number lk(c) of c equals 2 tan(f)-1 where
tan(f) is the tangential self-intersection number of f. We also show that if C
is convex and if the principal curvatures of S are suitably pointwise pinched
then the self-linking number of a periodic Reeb orbit of Maslov index 3 equals
-1.
