Qmd1[x_, rho_] :=
Module[{n,t},
If [rho < .3,
If [x < 9 + 15 Log[10, .3 / rho],
Qmd1series[x, rho],
Qmd1asymp[x, rho]
],
If [x > 8,
Qmd1asymp[x, rho],
Qmd1poly[x, rho]
]
]
]
(* needs also the definition of the functions
Qmd1asymp,
Qmd1poly and
Qmd1series *)