Catechism of the Catholic Church: here.

Compendium of the Social Doctrine of the Church: here.

Other Compendiums of Catholic Teaching: Sources of Catholic Dogma—Denzinger // Catechism of the Council of Trent // Fundamentals of Catholic Dogma—Ott // Documenta Catholica Omnia

Papal Magisterium: Vatican Website, here. // Papal encyclicals website, here.

U.S. Bishops: here.

National Catholic Bioethics Center: here.

St. Thomas Aquinas: here.