During the breach of the bomb-maker's lair, the phrase "Give me two" was stated: Military procedure when breaching a room, the lead will call out for X number to follow while the rest secure the room. In this case he says two because he needs two members of the team to apprehend the armed convicts, the one who sound off two are the responders while the rest continue with the room.
Cinque was the leader of the Symbionese Liberation Army (SLA) in the '70, a radical left organization which wanted to overthrow the capitalist economic system in the United States.
While interrogating Gelina, Hondo mentions cult leaders Jim Jones and David Koresh. As leader of the Peoples Temple, Jones was responsible for the mass suicide of his followers at his Jonestown settlement in 1978, which was the single greatest loss of American civilian life until the September 11 attacks in 2001; Koresh was the leader of the Branch Davidians, the target of the 51-day Waco siege in 1993, which ended with the now-famous conflagration of their compound, resulting in 76 deaths; Timothy McVeigh later cited the events at Waco as his motive for the 1995 bombing of a government building in Oklahoma City, which remains the deadliest incident of domestic terrorism in U.S. history.
When Commander Hicks and Mayor Barrett are talking to the CEOs debating about how to go about resolving the crisis, one of the CEO's is named 'Jeremy Dewitt'. The Irony of this is that name is synonymous with a very well known serial police impersonator from Florida who has been in countless instances of impersonating police and constant legal troubles.