Noncommutative algebras and noncommutative rings; OPERATORALGEBREN (FUNKTIONALANALYSIS); NICHTKOMMUTATIVE ALGEBREN UND NICHTKOMMUTATIVE RINGE (ALGEBRA); LINEARE DIFFERENZENGLEICHUNGEN (ANALYSIS); LINEAR DIFFERENCE EQUATIONS (MATHEMATICAL ANALYSIS); Linear difference equations; OPERATOR ALGEBRAS (FUNCTIONAL ANALYSIS); LINEAR ORDINARY DIFFERENTIAL EQUATIONS (MATHEMATICAL ANALYSIS); LINEARE GEWÖHNLICHE DIFFERENTIALGLEICHUNGEN (ANALYSIS); NONCOMMUTATIVE ALGEBRAS AND NONCOMMUTATIVE RINGS (ALGEBRA); Operator algebras; Linear ordinary differential equations