A second-half Filip Helander goal gave Rangers a 1-0 win over Celtic in the first Old Firm derby of the season.
Both sides were looking to close in on Edinburgh sides Hibs and Hearts above them, while it was a chance for Celtic to gain some revenge after Rangers won their first league championship in a decade last season.
Ange Postecoglou had his head in his hands midway in the first half when Odsonne Edouard dragged a shot wide from close range when it appeared easier to score.
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Celtic had a penalty appeal when it seemed that Leon Balogun touched the ball with his arm as he fell, but it may have been a harsh decision to award a spotkick.
Minutes later, Ryan Kent went the closest of any player on both teams when he struck the inside of the post with a curling, low shot.
The winner came when Helander converted a Borna Barisic cross from wide, beating Joe Hart who could only get fingers to the header.
The win leaves Rangers on nine points, a point off joint top, and Celtic end the week in sixth.
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