"frequently state" — Kollokationen-Wörterbuch Englisch

frequently state Kollokation
Beliebtere Konjugation: frequently stated
Automatische Übersetzung (wir garantieren seine Korrektheit nicht): często stan
  1. state Verb + frequently Adverb
    Schwache Kollokation

    Thus older sources frequently state that there are only four or five species.