The Guaraní language has been much cultivated, its literature covering a wide range of subjects. Many works were written by priests, either wholly or partly in the native language, and were published by the mission press in Loreto. Among the most important treatises on the language are the "Tesoro de la Lengua Guaraní" (Madrid, 1639) by Father Montoya, published in Paris and Leipzig in 1876; and the "Catecismo de la Lengua Guaraní" of Father Diego Díaz de la Guerra (Madrid, 1630).