  In this note we characterize 1+n doubly twisted spacetimes in terms of
`doubly torqued' vector fields. They extend Bang-Yen Chen's characterization of
twisted and generalized Robertson-Walker spacetimes with torqued and
concircular vector fields. The result is a simple classification of 1+n
doubly-twisted, doubly-warped, twisted and generalized Robertson-Walker
spacetimes.
