Name the 4 players that have played for both rangers and Celtic?

it was 6

1-Alfie Conn;-Rangers-Tottenham-Celtic 2.Maurice Johnston;- Partick Thistle-watford-Celtic-nantes-rangers 3.Stephen Pressley:-Rangers-Dundee Utd-Hearts-Celtic 4.Kenny Miller;- Hibs-rangers-wolves-celtic-derby-rangers 5.Barry robson - Rangers - Inverness CT(loan to forfar) - Dundee utd. Celtic. 6.Mark brown - Rangers - Motherwell - Inverness CT - Celtic