P 63,NR.173*CB*
LATT    -1
SYMM     -Y,   X-Y,     Z
SYMM    Y-X,    -X,     Z
SYMM     -X,    -Y, .5+Z
SYMM      Y,   Y-X, .5+Z
SYMM    X-Y,     X, .5+Z  
    0 .6666 / 0 .6666 / 0 .5
    SONDER: X .LE. (1+Y)/2
    SONDER: Y .LE. MIN. (1-X,(1+X)/2)
    P 63,NR.173*CB*