  For null curves in PSL(2,C), there exists a representation formula in terms
of two meromorphic functions and their derivatives (Small's formula). In this
paper, we give an elementary proof of Small's formula. Moreover, a similar
formula for Legendrian curves in PSL(2,C) is given. As null curves in PSL(2,C)
are related to mean curvature one surfaces in hyperbolic 3-space H^3,
Legendrian curves are related to flat surfaces in H^3. So, as an application of
Small-type formula for Lengendrian curves, we give new examples of flat
surfaces in H^3.
