and 
, 
are compact, then there is
a compact operator a such that 
.
HYOUNGSOON KIM
We prove the following unbounded generalization of the strong interpolation theorem [2, Corollary 3.16] under some extra hypotheses:
1. If h and k are self-adjoint operators on a Hilbert space H,
k is bounded, and , are compact, then there is
a compact operator a such that .
2. If h and k are self-adjoint operators on H, and
, are compact, then for all 
there is a compact
operator a such that 
.