@article{833066, author = {M Bradley and James Porto and S Rainville and J Thompson and D Pritchard}, title = {Penning Trap Measurements of the Masses of 133Cs, 87,85Rb, and 23Na with Uncertainties <0.2 ppb}, year = {1999}, number = {83}, month = {1999-01-01 00:01:00}, publisher = {Physical Review Letters}, language = {en}, }