He extended and increased the missions, creating new ones outside of Europe, especially in Japan. His book of forty-odd sermons for Lent, and his work of six folio volumes, In Selecta Scripturae Loca Ethicae Commentationes, demonstrate his scholarship and piety. Remembering what had happened to Cardinal Francesco Sforza Pallavicino, Oliva printed one thousand of his letters, in order that they might not be printed by others and be misconstrued.
He expanded the missions beyond Europe, including Japan. His Lent sermons and six-volume work, In Selecta Scripturae Loca Ethicae Commentationes, reflect his scholarly dedication and piety. Considering Cardinal Francesco Sforza Pallavicino's experience, Olivieri printed one thousand letters to prevent their unauthorized publication and misinterpretation.