A sacrament is a mystery in that it implies the presence of God in human actions.
Eph 5:32; 1 Tim 3:9
"You have shown Yourself to me,O Christ, face to face. I meet You in Your sacraments."
Saint Ambrose
There are three things that spread the Christ life to us: baptism, belief, and that mysterious action which different Christians call by different names - Holy Communion, the Mass, the Lord's Supper."
C.S.Lewis
Sacraments www.newadvent.org/cathen/13295a.htm
http://catholiceducation.org/articles/apologetics/ap0030.html
What Are Sacraments? www.americancatholic.org/Newsletters/CU/ac0895.asp
The Seven Sacraments http://jesuschristsavior.net/Sacraments.html
Seven Sacraments, One Mystery www.americancatholic.org/Newsletters/VAT/aq0504.asp
Sacraments: It All Starts With Jesus www.americancatholic.org/Newsletters/CU/ac0893.asp
The Sacraments as Sacred Signs and as a Means of Grace
www.catholicdoors.com/teaching/book2/2-1.htm
The Sacraments: Divine Channels of Grace
www.therealpresence.org/archives/Sacraments/Sacraments_002.htm
Sacramental Life Assures Eternal Life
www.therealpresence.org/archives/Sacraments/Sacraments_016.htm
The Sacraments: The Life of the Christian
www.catholicapologetics.org/ap060000.htm
www.catholicapologetics.org/Slides/Sacraments%20Part%201_files/frame.htm
The Celebration of the Christian Mystery - The Sacraments
www.scborromeo.org/ccc/p2s1c1a2.htm#1113
ON-LINE STUDY COURSE:
The Holy Spirit and the Sacraments www.catholicdoors.com/courses/th2.htm