How to select all units of specific types from a group in Starcraft 2

Say I have Marines, Wraiths and Siege Tanks selected in one group binded as group 1. Now what's the easiest way of i.e. selecting all Wraiths from the group so can I can quickly cloak them. I know I could assign them to different group but I don't want to do that.

From gaming RaYell

• There is a certain key combination to cycle through subgroups in a group. Something with TAB.

  Alternatively you could double-click on one unit which selects all units of the same type.

  McKay : ++ Yeah, if all you want to do is cloak the units of one type, this is definitely the preferred solution.

  Lee : Tab on its own cycles through unit types in a control group.
  From StampedeXV

• You can ctrl+click the unit in the hud. That will select the same type of unit in the group even if they are not visible on screen.

  Lee : Ctrl+click and double click are interchangeable, both on the ground and the HUD. I mention this because I find double clicking to be faster.
  From Grzegorz Adam Hankiewicz