Gram's law (Hutchinson 1925; Edwards 2001, pp. 125, 127, and 171) is the tendency for zeros of the Riemann-Siegel function 
to alternate with Gram
points. Stated more precisely, it notes the tendency for 
to hold, where 
is a Gram point.
Strictly speaking, the statement "
" should perhaps be called the weak Gram's
law since Hutchinson (1925) used the term "Gram's law" to refer to the
stronger statement that there are precisely 
zeros of 
between 0 and 
(Edwards 2001, p. 171).
