Former UN Secretary General Kofi Annan announced today that Kenya's rival political parties have agreed on a plan to end the violence. Violence has flared in the country since the disputed presidential election in December. Some of the worst violence has occurred in Nairobi's Kibera slum. Anchor Lisa Mullins speaks with Robert Neuwirth, author of the book, "Shadow Cities: A Billion Squatters, A New Urban World." Neuwirth lived in Kibera for several months while researching his book.