@article{10_4064_sm180_3_2,
     author = {Hong-Ke Du and Chun-Yan Deng and Mostafa Mbekhta and Vladim{\'\i}r M\"uller},
     title = {On spectral properties of
 linear combinations of idempotents},
     journal = {Studia Mathematica},
     pages = {211--217},
     publisher = {mathdoc},
     volume = {180},
     number = {3},
     year = {2007},
     doi = {10.4064/sm180-3-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm180-3-2/}
}