@article{10_1017_S0017089500002214,
     author = {Mocanu, GH.},
     title = {On the numerical radius of an element of a normed algebra},
     journal = {Glasgow mathematical journal},
     pages = {90--93},
     year = {1974},
     volume = {15},
     number = {1},
     doi = {10.1017/S0017089500002214},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089500002214/}
}