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 *)