'Unacceptable' that Rangers did not get penalty - Collum - Scottish refs 'are improving' as Collum makes tournament vow - Collum urges caution over referees' mental health - VAR stays, says Mulraney, as Collum backed to fix flaws - VAR stays, says Mulraney, as Collum backed to fix flaws - Collum called out over 'angry' Celtic vs Rangers exchange - Collum called out over 'angry' Celtic vs Rangers exchange