Thisexpositorymonographwaswrittenforthreereasons. Firstly, wewantedto present the solution to a problem posed by Wolfgang Krull in 1932 Krull 32]. He asked whether what we now call the "Krull-SchmidtTheorem" holds for - tinianmodules. Theproblemremainedopenfor63years: itssolution, anegative answer to Krull's question, was published only in 1995 (see Facchini, Herbera, Levy and Vamos]). Secondly, we wanted to present the answer to a question posed by War?eld in 1975 War?eld 75]. He proved that every ?nitely p- sented module over a serial ring is a direct sum of uniserial modules, and asked...