Comment on the quantum nature of angular momentum using a coupled-boson   representation
  A simple approach for understanding the quantum nature of angular momentum and its reduction to the classical limit is presented based on Schwinger's coupled-boson representation. This approach leads to a straightforward explanation of why the square of the angular momentum in quantum mechanics is given by j(j+1) instead of just j^2, where j is the angular momentum quantum number. 
ILki Kim, Gerald J. Iafrate