Multiple non-thunderbolt monitors to MBP-r '12

Does anyone know if it's only possible to add 3 external monitors if at least one of these is a thunderbolt display?

I'm asking since I would love to hook up 3 Dell monitors to my macbook at work. Connection options are HDMI, DP VGA and DVI only.

Currently I have one connected with HDMI and one with VGA - works both with the built-in HDMI port and the minidp -> hdmi adapter.