FEMTOVOLTMETER AND VOLTAGE TUNABLE HETERODYNE RECEIVER BASED ON THE dc RESISTIVE SQUID B.T. Ulrich, R.W. Van der Heijden et J.M.V. Verschueren J. Phys. Colloques, 39 C6 (1978) C6-1221-C6-1222 DOI: 10.1051/jphyscol:19786540