@article{01796008,
title = {Infinite dimensional extension of A. P. Calder\`on's theorem on positive semidefinite biquadratic forms.},
journal = {Lobachevskii Journal of Mathematics},
volume = {10},
year = {2002},
pages = {3-8},
zbl = {1003.46013},
language = {en},
url = {http://dml.mathdoc.fr/item/01796008}
}
Aqzzouz, B.; El Kadiri, M. Infinite dimensional extension of A. P. Calderòn's theorem on positive semidefinite biquadratic forms.. Lobachevskii Journal of Mathematics, Tome 10 (2002) pp. 3-8. http://gdmltest.u-ga.fr/item/01796008/