For the theory, see chapter 'Letterplace' in the @sc{Singular} Manual
Support: Joint projects LE 2697/2-1 and KR 1907/3-1 of the Priority Programme SPP 1489:
'Algorithmische und Experimentelle Methoden in Algebra, Geometrie und Zahlentheorie'
of the German DFG
and Project II.6 of the transregional collaborative research centre
SFB-TRR 195 'Symbolic Tools in Mathematics and their Application' of the German DFG