Roup Psychology and the Analysis of the Ego

The assignment is following:

Freuds Group Psychology and the Analysis of the Ego is perhaps Freud s fundamental work on collective psychology. What is the main function that holds together the individuals in a group, creates the groups forms, ensures its continuity and stability, or causes its disappearance? Define  identification according to Freud. Explain the differences between love and identification.

Tips:
Define group (mass) psychology according to Freud. (Freud offers more than one definition).
Define libido and how does Freud relate it to love and the soul of the mass.
Which is the role played by the ideal and identification in the mass?