Nanoparticles superficial density of charge in electric double-layered magnetic fluid: A conductimetric and potentiometric approach A.F.C. Campos, F.A. Tourinho, G.J. da Silva, M.C.F.L. Lara and J. DepeyrotEur. Phys. J. E, 6 1 (2001) 29-35DOI: https://doi.org/epje/v6/p29(epje01068)