The aim of this monograph is the exact description of minimal smooth algebraic surfaces over the complex numbers with the invariants $K DEGREES2 = 7$ und $p_g = 4$. The interest in this fine classification of algebraic surfaces of general type goes back to F. Enriques, who dedicates a large part of his celebrated book Superficie Algebriche to this problem. The cases $p_g = 4$, $K DEGREES2 \leq 6$ were treated in the past by several authors (among others M. Noether, F. Enriques, E. Horikawa) and it is worthwhile to remark that already the case $K DEGREES2 = 6$ is rather complicated and it is up to now not possible to decide whether the moduli space of these surfaces