/GrADS/script/clave.gs
/ 
clave
var_in time1 time2
(ystart yend | -ylist y1,y2,...)
[var_out]
[-within]
ga-> clave u 01jan%y %endjan%y 1980 1989
ga-> clave ps 01dec%y %endfeb%ypp 1970 1999 clps
ga-> d clps
ga-> clave u dec%y feb%ypp 1990 1999 -within