The following statements are available in PROC BTL.
                         PROC BTL
                          <options>   ; 
                         BY
                          variables   ; 
                         CLASS
                          variables   ; 
                         MARKER
                          variables </ options>   ; 
                         MODEL
                          dependent <= fixed-effects> </ options>   ; 
                         PARMEST
                          <options>   ; 
                         PARMS
                          (value-list) …</ options>   ; 
                         RANDOM
                          random-effects </ options>   ; 
                         REPEATED
                          <repeated-effect> </ options>   ; 
                         WEIGHT
                          variable   ; 
            
Items within angle brackets (<> ) are optional. The RANDOM statements can appear multiple times; all other statements can appear only once.
The PROC BTL, MARKER, and MODEL statements are required, and the MODEL statement must appear after the CLASS and/or MARKER statement if either or both statements are included. The RANDOM and REPEATED statements must follow the MODEL statement.