Celtic returned to within four points of Scottish Premier League leaders Rangers after beating Dundee United.
The visitors dominated early on and Gary Hooper's 12th-minute strike broke the deadlock.
James Forrest failed to convert an excellent chance and Cha Du-Ri fired wide as Celtic continued to press in the first half.
United rarely threatened and were poor in possession throughout, a wayward shot by Willo Flood their best effort.
Traffic problems near Tannadice meant a change of referee with Calum Murray unable to make it to the ground on time and Craig Thompson stepping up from his fourth official role.
Celtic were on the attack straight away and Georgios Samaras burst down the left before firing across a low centre that Anthony Stokes was inches away from connecting with.
The visitors were pinning United back and Forrest skilfully evaded John Rankin and crossed for Stokes, whose header looped over the crossbar.
It was the turn of the Tangerines to exert some pressure and driven crosses by Rankin and Robbie Neilson required last-ditch clearances from the visiting defence.
Chances became far and few between as the game wore on
But Celtic soon opened the scoring with Hooper and Forrest combining well on the break.
The striker received Forrest's return pass, skipped past Gavin Gunning and slammed a shot across the bows of goalkeeper Dusan Pernis into the far corner.
Forrest then played a one-two with Stokes to beat the offside trap but the winger planted his shot straight into the arms of Pernis.
Neilson ventured foward to boost Dundee United's attack and managed to get a header to Rankin's cross but keeper Fraser Forster gathered.
United's frustration at having so few chances was demonstrated by Johnny Russell's hurried shot from distance that flew wide when playing in a teammate would perhaps have been a better option.
Another Celtic one-two, this time between Cha and Hooper, put the defender through but his shot was well wide.
The home side's inability to retain meaningful possession continued after the break but Celtic were doing little to turn their superior territory into a more convincing lead.
United manager Peter Houston decided to take action and sent on Lauri Dalla Valle and Stuart Armstrong in place of Gary MacKay-Steven and Scott Robertson.
Celtic boss Neil Lennon also made a change with Glenn Loovens withdrawn and club captain Scott Brown continued his return from injury from the bench, Victor Wanyama dropping back into defence.
Flood's inswinging corner was beaten away by Forster as the game became ever more scrappy.
Flood then blazed wide from a promising position and that proved to be the midfielder's last contribution as Ryan Dow came on in his place.
At the other end, Forrest was also off target with two efforts from the left as Celtic closed out the game.
Dundee United 01 Pernis 03 Dixon 05 Kenneth 18 Gunning 26 Neilson Booked 06 Flood (Dow - 83' ) 08 Robertson (Dalla Valle - 61' ) 11 Rankin Booked 17 Mackay-Steven (Armstrong - 61' ) 09 Daly 15 Russell Substitutes 13 Banks 02 Dillon 12 Watson 14 Douglas 16 Armstrong 19 Dalla Valle 22 Dow Celtic 01 Forster 05 Majstorovic 11 Cha Du-Ri 22 Loovens (Brown - 67' ) 02 Matthews 33 Kayal 67 Wanyama 09 Samaras 10 Stokes (Ki Sung-Yeung - 78' ) 49 Forrest 88 Hooper Substitutes 24 Zaluska 56 Twardzik 08 Brown 18 Ki Sung-Yeung 20 McCourt 46 McGeouch 14 Bangura
Ref: Craig Thomson