"The Church's social teaching is a rich treasure of wisdom about building a just society and living lives of holiness amidst the challenges of modern society. Modern Catholic social teaching has been articulated through a tradition of papal, conciliar, and episcopal documents. The depth and richness of this tradition can be understood best through a direct reading of these documents. "
In most cases, searching the phrase "Catholic Social Teaching" will result in a great number of results. Catholic Social Justice or Catholic Social Thought are other possible phrases.
Here are some other terms that you may use to narrow your search, depending upon the specific subject of your research:
poverty common good
"preferential option for the poor" solidarity
human dignity justice
euthanasia third world
capital punishment hunger