1. Fouad Nakhli,
$$e^{\pi }>\pi ^{e}$$
e
π
>
π
e
, Mathematics Magazine, 60(3) (1987), pp. 165.
2. Roger B. Nelsen, Proofs without Words: Exercise in Visual Thinking, The Mathematical Association of America, 1993.
3. Roger B. Nelsen, Proofs without Words II: More Exercise in Visual Thinking, The Mathematical Association of America, 2000.