Gravitational mass versus circumferential radius for slowly rigidly rotating NSs (with the same period as that of the Crab pulsar) for the Brussels-Montreal EoSs based on the EDFs BSk19-20-21, and for the SLy EoS based on the SLy4 EDF. The thick dashed lines labelled by 2.8 M_⊙, 4.6 M_⊙, and 6.4 M_⊙ correspond to the constraint in Eq. (6) (see text for details); the region below each line is excluded. The shaded area in the top left-hand corner, delimited by R > 2.9GM/c², is excluded by causality (Glendenning 2000).