[lammps-users] problem using Improper style

I am trying to simulate Boron nitiride nanotube with water, so I have to use improper style hybrid umbrella cvff.
but its complaining that invalid improper style.
please tell me how to which of improper style can be replaced by umbrella.

LAMMPS has 3 improper styles currently implemented. The doc
pages have the relevant formulas. Which ones do you
want to use with improper_style hybrid? "Umbrella" is not
a style name LAMMPS uses.

Steve