@article{10_1017_S0017089599000543,
     author = {Duggal, B.P.},
     title = {A {Putnam} area inequality for thespectrum of n-tuples ofp-hyponormal operators},
     journal = {Glasgow mathematical journal},
     pages = {385--391},
     year = {1999},
     volume = {41},
     number = {3},
     doi = {10.1017/S0017089599000543},
     url = {http://geodesic.mathdoc.fr/articles/10.1017/S0017089599000543/}
}