DS 2866. Cf. also W. Most, "Religious Liberty: What the Texts Demand" in Faith & Reason 9 (1983) pp. 196-209. Further clarification of the fact that Vatican II does not clash with Pius IX (cf. p. 206) is this: Vatican II, in # 7 did make provision for more than just public order when it said that the state must exercise "due custody for public morality," and in #4 it said that the churches must abstain from any action that would involve "improper persuasion aimed at the less intelligent or the poor." Pius IX had said (cf. p. 201) that the state must do more than merely defend public order in regard to excesses in religious liberty.
NB: These notes are also displayed as endnotes at the bottom of every chapter.