I think the virtual ground here acts as a ground for the whole circuit, an the shown schematic is just to get dual supply voltage of ±10V .
. If you want to use a voltage source you have two approaches:
1. You can use dual supplies 10V and -10 with their common ground at VGND. i.e. Two Chips, 7810 and 7910, with the ground node at VGND.
2. OR Do the circuit as usual but the virtual ground is just a floating node from which you get your output not the usual supply ground.i.e. with one supply of +20V get the node VGND and connect it to the ground node of your circuit, and keep the negative node or the ground node of the source away from VGND.