Universality of mod-p cohomology

Let p be an odd prime number. We relate the algebraic notion of a mod-p formal group law and the topological notion of a mod-p oriented ring spectrum. It is shown that there exists a universal mod-p oriented ring spectrum MOp which splits as a wedge sum of Eilenberg–MacLane spectra. The mod-p Eilenberg–MacLane spectrum is shown to be the universal mod-p oriented ring spectrum with an additive mod-p formal group law.