combination_with_repetition
                        Combination with repetition.
estprod_data            10000 randomly generated variables in panel
                        data format.
levinsohn_petrin        Levinsohn-Petrin Estimation of Production
                        Functions
olley_pakes             Olley-Pakes Estimation of Production Functions
panel_lag               Panel data lag function
poly_elements           Number of 'poly' elements.
wooldridge              Wooldridge Estimation of Production Functions
                        (Cobb-Douglas)
