This document discusses single sign-on (SSO) with TYPO3 CMS and provides examples of real-world SSO implementations. It describes five case studies of SSO projects involving integration with Windows Active Directory, SAP, OpenSSO, Shibboleth, and using TYPO3 as the authentication master. The document outlines important considerations for SSO projects, such as infrastructure requirements, authorization vs. authentication, and coordinating complex project teams. No two SSO projects are alike and implementing SSO requires coordinating many participants to address technical and organizational challenges.