Book:Article/Bernhard Riemann/Ueber die Anzahl der Primzahlen under einer gegebenen Grösse

Subject Matter
In this thesis, investigates 's definition of the Zeta function:
 * $\displaystyle \sum_{n \mathop \ge 1} \frac 1 {n^s} = \prod_p \dfrac 1 {1 - p^{-s} }$

where the product ranges over all primes $p$.

recognised that the deeper questions about distribution of primes can be investigated only by $s$ being a complex variable.