Revealing common artifacts due to ferromagnetic inclusions in highly oriented pyrolytic graphiteaM. Sepioni, R. R. Nair, I.-Ling Tsai, A. K. Geim and I. V. GrigorievaEPL, 97 4 (2012) 47001DOI: https://doi.org/10.1209/0295-5075/97/47001