Why aren't the points to the left and right of \$R_1\$ and \$R_2\$, respectively, nodes?
They are nodes a and e respectively.

Node a connects R1, R3, R6, and two unnamed current sources.
Node e connects R2, R5, a current source and a voltage source.

Trace ALL the wires out from a node name until you reach a component : don't just stop when you reach an anonymous dot.