Comparison of the primary and secondary antiphospholipid syndrome: a European multicentre study of 114 patients - Vianna, J L; Khamashta, M A; Ordi-Ros, J; Font, J; Cervera, R; Lopez-Soto, A; Tolosa, C; Franz, J; Selva, A; Ingelmo, M; Vilardell, M; Hughes, G R V (Am J Med, 1994)