Celtic moved six points clear at the top of Ladbrokes Premiership on Sunday with a 2-0 win over St Johnstone at McDiarmid Park thanks to late goals by James Forrest and substitute Timothy Weah.

Here, Press Association Sport examines five key lessons learned from the weekend's top-flight action.

Celtic find a way to win

Celtic left it late to regain their six-point lead at the top of the Ladbrokes Premiership. The home side missed two early chances before the Hoops dominated possession, forcing Saints keeper Zander Clark into a series of saves in the second-half and it looked like the home side could hold out. However, the champions kept going and winger Forrest broke the deadlock in the 78th minute before Weah, on for injured fellow substitute Odsonne Edouard, notched in the 89th minute to clinch the victory and give the champions a crucial cushion.

No end to referee controversy

Refereeing standards have questioned for much of the season in Scotland and there was more controversy sparked when referee Andrew Dallas awarded Rangers a remarkable four penalties in the 4-0 win over St Mirren at Ibrox on Saturday. Gers captain James Tavernier scored two and missed one with striker Jermain Defoe scoring his first Ibrox goal from the spot as Ryan Kent chipped in with  fourth goal. St Mirren boss Oran Kearney was far from impressed by Dallas's performance and the fall-out will go on all week and beyond.

Hearts back on form

Craig Levein's side started the season in impressive form, forcing their way to the top of the table. However, results took a dip and they slid back down the table. But the Jambos' 2-1 victory over in-form Kilmarnock at Rugby Park on Friday night  thanks to goals from Sean Clare and Steven Naismith gave them their fifth win in six games and confirmed the confidence is back in Gorgie.

Stewart back to his best

Greg Stewart has a central role for Aberdeen The on-loan Birmingham player had a far more fruitful spell at Kilmarnock before New Year – scoring eight goals from a central role – than he did at Pittodrie last season. The former Dundee player normally played wide and netted four times last campaign, and Derek McInnes seems to have paid heed to the difference. The Dons boss put Stewart at the heart of a three-man strikeforce in a 2-1 win over Hibs with the width coming from deeper and his recent signing was influential.

Motherwell benefit from tactical switch

Motherwell have adapted to their new style of play, with manager Stephen Robinson employing two wingers and ditching his three-man central defence – to be rewarded with three consecutive wins. The Motherwell boss had warned the shift in approach could take time but they blew away Livingston inside 21 minutes to wrap up a 3-0 win. Wide player Jake Hastie has been crucial in the transformation since returning from a loan stint at Alloa and he hit a double against Livi.