Trattato di Sociologia Generale (excerpt: first dozen pages)
(engl., ed.: Mind and Society, Donver 1935)
at Marxists Internet Archive
[marxists.org/reference/subject/philosophy/works/it/pareto.htm]

The New Theories of Economics (article)
(engl.)
at McMaster University
[socserv.mcmaster.ca/econ/ugcm/3ll3/pareto/theories]