Manchester City and Liverpool have written to their supporters to urge them to behave themselves at this weekend's fixture between the two rivals.
Both sides face off at the Etihad Stadium in a match that kicks-off at 12.30pm after police - concerned over trouble - refused permission for it to start at 5.30pm.
And, in a further move, Mail Sport understands that officials have now been in touch with supporters who have tickets ahead of the match.
Liverpool have referenced missile throwing, while City have highlighted tragedy chanting, with both messages warning fans that action will be taken against those found to have misbehaved.
Games between the two clubs have been marred by issues in what is a growing rivalry that has, in recent times, turned toxic.
The match will be televised. Mail Sport previously revealed Sky bosses had eyed the prime-time 5.30pm slot.
However, the local safety advisory group - which includes the police - were not expected to give permission and so it was brought forward to the 12.30pm slot after an agreement was reached with TNT Sports, who usually show the earlier game.
Liverpool's allocation was cut for last season's match at the Etihad from 3,000 to 2,400. This time, there has again been a reduction, but to a lesser extent. The original move was made in the wake of a number of incidents of trouble which included a 15-year-old girl being left 'scarred for life', when she was struck by a pot filled with coins that had been hurled from the visitors' section at a December Carabao Cup clash.
More than 50 reports of missiles being launched from the away end were made at that fixture, while a City fan was ejected and arrested after being accused of abusing disabled Liverpool supporters.
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