Direct imaging of light-element impurities in graphene reveals triple-coordinated oxygen oleh Christoph Hofer, Viera Skákalová, Tobias Görlich, Mukesh Tripathi, Andreas Mittelberger, Clemens Mangler, Mohammad Reza Ahmadpour Monazam, Toma Susi, Jani Kotakoski, Jannik C. Meyer