Here are some helpful articles on these topics:
Sabbath and Sunday
From Sabbath to Sunday: How the Church Moved Its Holy Day, James P. Guzek, This Rock, February 1999.
The Catholic Encyclopedia: "Sunday"
Sabbath or Sunday: What Does Holy Scripture Say?, Bob Stanley
On Keeping the Lord's Day Holy (Dies Domini): Apostolic Letter of Pope John Paul II (31 May 1998)
Sunday Obligation to Attend Mass
Why Is It a Mortal sin to Miss Mass?, Fr. Ray Ryland, This Rock, July 2000.
Forget Mass? Not a Mortal Sin, Karl Keating, This Rock, Nov. 2003.
FAQ About Sunday Obligation: Not Going to Mass (Catholic Doors Ministries)
Sunday Obligation, Jimmy Akin
Fulfilling the Sunday Obligation on Saturday (+ Part Two), Jimmy Akin
Our Sunday Obligation, Maureen Kelly
There Are Reasons to Miss Mass, but Not Many Valid Ones, Fr. Matthew Mitas
See also The Catechism of the Catholic Church: #2168-2195.
