Our approach provides an alternative derivation of the functional equation.
For our purposes here, the best way is to base the proof on the following theorem, a derivation of which can be found in [P].
Go to the list of words starting with: a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
y
z