Where would I attach ground to?

[CDCosma]

Hi, I'm making a Transistor NOR gate based off the circuit found here:
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/trangate.html#c5
Where would I attach ground to coming from the emitter of the transistor?

 

[Harald Kapp]

Ground is at the Emitter. It's the tree-dashes symbol. It's connected to the minus pole of the battery.

Harald