Four more Sunderland players earn international call-ups ahead of Euro 2020 qualifiers
Michael O'Neill has named a 27-man squad to face Estonia in and Belarus later this month.
Both games will be held in Belfast, with Estonia set to visit Windsor Park on March 21, before the clash with Belarus three days later.
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Hide AdGrigg, 27, wasn't included in the previous squad due to injury but could now add to his 13 international caps.
Flanagan, too, missed the Nations League game against Austria and the friendly against the Republic of Ireland back in November.
Sunderland goalkeeper Jon McLaughlin and winger Lewis Morgan have also been called-up to Scotland's 27-man squad.
Alex McLeish's side will face an away trip to Kazakhstan before travelling to San Marino three days later.
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Hide AdThe pair won't miss any League One fixtures for Sunderland after the Black Cats' game at Fleetwood was postponed.
Aiden McGeady and Jimmy Dunne were also induced in the provisional Republic of Ireland squad last week.