  The notions of consistent pairs and consistent chains of t-structures are
introduced. A theorem that two consistent chains of t-structures generate a
distributive lattice is proven. The technique developed is then applied to the
pairs of chains obtained from the standard t-structure on the derived category
of coherent sheaves and the dual t-structure by means of the shift functor.
This yields a family of t-structures whose hearts are known as perverse
coherent sheaves.
