Scotland boss Gordon Strachan has handed first call-ups to Celtic's Stuart Armstrong, Bournemouth's Ryan Fraser and Fulham's Tom Cairney.The trio are included in a 30-man squad for the upcoming friendly against Canada and the World Cup qualifier against Slovenia.There is a recall for Hull goalkeeper Allan McGregor, who has impressed while on loan at Cardiff.Celtic captain Scott Brown, who reversed his decision to retire from international football last year, is also included. However, there is no place for the likes of Graeme Shinnie and Kenny McLean of Aberdeen. Armstrong, capped 20 times by the Under-21s, has forced his way into the reckoning after discovering his shooting boots in recent months. The 24-year-old has scored 11 times for Celtic this season, eight times since the start of December. Fraser's form has also been impressive over the winter. The 23-year-old made his mark in the Cherries' remarkable 4-3 comeback win over Liverpool in December, coming on as a second-half substitute with his side 2-0 down before winning a penalty for Bournemouth's opener and scoring the second - his first goal for the club. Cairney, 26, was previously capped at Under-19 and Under-21 levels but has been made to wait for his chance with the seniors. But he has caught the eye in the Championship this season with Fulham, and scored a fine volley in the Cottagers' upset victory over leaders Newcastle at the weekend.McGregor is back in the squad almost a year after his last appearance - which came in the 1-0 win over the Czech Republic on March 24. Scotland take on Canada at Easter Road on March 22 before the World Cup qualifier against Slovenia at Hampden Park four days later.