I see that it is proven by Hardy in 1914 that there are an infinite number of zeros on the critical line. I also see that the Hardy and Littlewood conjectures appear in some papers they wrote together in 1921. However, it was further proven by Littlewood alone that if $\gamma_n$ is an increasing sequence of the imaginary parts of the zeros on the critical line in the upper complex half-plane then
$$ \lim\limits_{n\to\infty}|\gamma_n-\gamma_{n-1}| =0 ~~.$$
Can someone please give me the citation for the paper in which Littlewood proved this result on his own? I absolutely cannot find it!
@Article{LW, author = "J.E. Littlewood", title = "Two notes on the {R}iemann {Z}eta-function", journal = "Math. Proc. Camb. Phil. Soc, 22, 3, 234-242 ", year = "(1924)",}