Paragraph two, sub-section 'B' of the football's unwritten rule book says that Preston North End don't lose to Bristol City.
Their victory as Ashton Gate on Tuesday night was a ninth game unbeaten for PNE against the Robins, a record stretching back to 2011.
It ended North End's two-month wait for a win, goals from Paul Gallagher and substitute Callum Robinson securing the three points in the west country.
An injury-time goal from Cauley Woodrow was to prove only a consolation, Alex Neil's men hanging on to see a good job done.
At times they had to dig in and battle but no one could begrudge them the win at this happy hunting ground - they have won here four seasons in a row.
Gallagher struck in the 44th minute to put PNE in front, that the midfielder's first goal for 13 months.
Robinson, who replaced Gallagher after an hour, struck the second 12 minutes from time as North End counter-attacked in style, Jordan Hugill and Tom Barkhuizen linking-up to set up the goal.
Darnell Fisher was superb for Preston on his return to the side, with Ben Davies and Daniel Johnson impressive too.
Neil had made four changes to the side which drew with Bolton last Friday, Davies, Fisher, Johnson and Hugill returning to the starting XI.
Davies' return came just 24 days after surgery to remove his appendix, with Fisher back following a groin strain.
North End switched to a 4-4-2 formation from their usual 4-2-3-1 system, matching-up with that of the Robins.
They were bright early on, Paul Huntington putting a header wide inside the first two minutes after meeting a Gallagher free-kick, while Hugill should have done better after Johnson's pass played him into space down the right hand side of the box.
But his ball into the middle was neither a cross nor shot, keeper Frank Fielding getting down to gather.
A drilled centre from Fisher hit Barkhuizen and looped up over the bar as the visitors maintained their early pressure, then Hugill drew a save from Fielding with a shot from 20 yards.
Davies produced a double block to thwart the home side in the 17th minute.
When Chris Maxwell failed to hold a ball pumped high into the box, it fell to Jamie Paterson, his shot hacked clear by Davies.
Aden Flint's powerful follow-up drive was goalbound until it struck Davies on the chest and bounced clear, the home side's shout for handball falling on deaf ears.
Huntington and Ben Pearson needed treatment after the team-mates clashed heads attempting to make a clearance - the unstoppable force meeting the unmovable object as one PNE fan described it on social media!
Johnson saw a shot blocked by former North Ender Bailey Wright, his second attempt curling inches wide.
PNE finally made the breakthrough in the 44th minute, their first goal in 338 minutes.
Fisher drove up field from the right-back position and played the ball up to Hugill on the edge of the box.
Hugill's shot was charged down, the ball rebounding back against him and falling in the direction of Gallagher who spun and fired a right-foot shot into the corner of the net from 12 yards.
City made two substitutions at the interval and within the first 15 minutes of the second half, North End had made a couple of changes themselves with Alan Browne replacing Stephy Mavididi and Robinson joining the action in place of goalscorer Gallagher.
Just past the hour, Barkhuizen cleared off the line from a Niclas Eliasson header at a corner, Maxwell claiming he had been impeded as the ball came over.
Pearson's foul on Joe Bryan earned him a yellow card and a costly one at that, it being his fifth of the season which rules him out of Saturday's visit to Norwich.
In the 72nd minute, Johnson's pass found Pearson 25 yards out, the midfielder's shot parried by Fielding before the keeper held the ball at the second attempt.
North End doubled their advantage in the 78th minute with a fine move on the counter-attack.
Hugill collected a pass from Barkhuizen just inside the City half before playing it back to the winger into space down the right.
Barkhuizen showed a clean pair of heels to the home defence and sent a low cross on the run into the box which Robinson slid in to meet with his out-stretched left boot and steer it across the keeper.
In stoppage-time, Maxwell made a great save from Bobby Reid, making himself big to block a shot from four yards.
But the keeper was beaten in the 94th minute, substitute Woodrow rifling home a shot from 10 yards.
Thankfully for North End, it came too late to be no more than a consolation and they saw out the last 90 seconds of added-on time to see the job through - Tom Clarke joining the action after the goal to help with that.
Bristol City: Fielding, Wright, Flint, Baker, Bryan (Woodrow 67), Paterson (Pack 46), Smith, Brownhill, O'Dowda, Reid, Djuric (Eliasson 46). Subs (not used): Taylor, Magnusson, Leko, Steele.
PNE: Maxwell, Fisher, Huntington, Davies, Woods, Gallagher (Robinson 61) Pearson, Johnson, Barkhuizen, Mavididi (Browne 55), Hugill (Clarke 90). Subs (not used): Harrop, Welsh, O'Connor, Rudd.
Referee: Darren Bond (Wigan)
Attendance: 17,355 (373 PNE)