series ~ Form(~edges + gwesp(0.25, fixed = TRUE) + nodecov("evcent_lag_sqrt") + 
    absdiff("evcent_lag_sqrt") + nodecov("tech_size_lag_sqrt") + 
    absdiff("tech_size_lag_sqrt")) + Persist(~edges + gwesp(0.25, 
    fixed = TRUE) + nodecov("evcent_lag_sqrt") + absdiff("evcent_lag_sqrt") + 
    nodecov("tech_size_lag_sqrt") + absdiff("tech_size_lag_sqrt"))
