 Complete the following phrase:  In his Untersuchungen zur spätbyzantinischen Verfassungs- und Wirtschaftsgeschichte, the German scholar Ernst Stein proposed that in the early 14th century, the megas logothetēs also exercised the functions of the former Eparch of Constantinople in overseeing the administration of the imperial capital, until Andronikos III Palaiologos , seeking to secure his throne after winning the 