| #### 7.10.2.8 crystallographicGroupPM Procedure from library `fpalgebras.lib` (see fpalgebras_lib). Usage: crystallographicGroupPM(d); d an integer Return: ring Note: - the ring contains the ideal I, which contains the required relations - pm group with the following presentation < x, y, m | [x, y] = m^2 = 1, m^(-1)*x*m = x, m^(-1)*y*m = y^(-1) > - d gives the degreebound for the Letterplace ring Example:
    LIB "fpalgebras.lib";
    def R = crystallographicGroupPM(5); setring R;
    I;
    ==> I[1]=y*x+x*y+1
    ==> I[2]=y*x+x*y+m*m
    ==> I[3]=m*m+1
    ==> I[4]=m*x*m+x
    ==> I[5]=m*y*m+Y
    ==> I[6]=x*X+1
    ==> I[7]=X*x+1
    ==> I[8]=Y*y+1
    ==> I[9]=y*Y+1

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