Dom Godefroid Belorgey, in his book, The Practice of Mental Prayer, discusses the stages of prayer, from the ordinary degrees of prayer, including meditation and affective prayer, to the mystical degrees, leading to spiritual marriage, while drawing on the tradition of the Church. Dom Belorgey was auxiliary superior of Citeaux between 1932 and 1952.
Dom Jean-Baptiste Chautard’s The Soul of the Apostolate discusses the necessity of the inner life of prayer in maintaining a successful active apostolate. Pope St. Pius X is quoted as saying that he chose this as his bedside book. Dom Chautard was Abbot of Notre Dame de Sept-Fons, in France, from 1899 until his death in 1935.