2959c81e_ufficient_Mating_Material_Rule__2
[0] Example E [2] 
This position is drawn, no side can mate the other since all the bishops control the same color squares. The number of bishops doesn't matter if they are all on same color squares of the board. If white could take black's bishops, or black could take white's bishop, the situation would be the same, the game is would remain drawn. If there were at least one bishop on different color, the game couldn't be terminated in draw, because mate is possible.
[E4EC] The insufficient Mating Material Rule
2