  We have proposed in previous papers that the high-frequency pair QPOs
observed in black-hole binaries with frequency ratio 3:2 are inertial-acoustic
oscillations (nearly horizontal oscillations with no node in the vertical
direction) or g-mode oscillations, which are resonantly excited on warped
relativistic disks. The resonance occurs through horizontal motions. In this
model the dimensionless spin parameter $a_*$ of the central sources can be
estimated when their masses are known from other observations. This estimate is
done for three sources (GRO J1665-40, XTE J1550-564, GRS 1915+105). For all of
them we have $a_*\leq 0.45$.
