span_bj                 Britten–Jones Tangency-Portfolio Spanning Test
                        (1999)
span_f1                 F1 Alpha-Spanning Test (Intercepts Only)
span_f2                 F2 Variance-Spanning Test (Slopes Only)
span_gl_a               Gungor–Luger Alpha-Only Spanning Test (2016)
span_gl_ad              Gungor–Luger Joint Mean–Variance Spanning Test
                        (2016)
span_grs                Gibbons–Ross–Shanken (GRS) Alpha Spanning Test
                        (1989)
span_hk                 Huberman–Kandel Joint Mean–Variance Spanning
                        Test (1987)
span_km                 Kempf–Memmel GMVP Spanning Test
span_py                 Pesaran–Yamagata Alpha Spanning Test (2024)
