2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179631We present model independent constraints on the masses and couplings to fermions of $B$ and $L$ conserving leptoquarks. Such vector or scalar particles could have masses below 100 GeV and be produced at HERA; we list the generation dependent bounds that can be calculated from rare lepton and meson decays, meson-anti-meson mixing and various electroweak tests. PLEASE NOTE: this file does not contain tables and figures, so is not very useful. Complete paper available (by mail) from sacha@physics.berkeley.edu.39 pages, CfPA 93-th-29High Energy Physics - Phenomenologytext