Matt 28:19  Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:

He used TITLES, "Father, Son and Holy Ghost."  But He noted that a single NAME was common to all three of these TITLES.  And it was that NAME they were to pronounce.

When you find where the apostles obeyed this command of Jesus in the Book of Acts, you read what that name was:

Acts 2:38  Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.

Acts 8:16  (For as yet he was fallen upon none of them: only they were baptized in the name of the Lord Jesus.)

Acts 10:48  And he commanded them to be baptized in the name of the Lord. Then prayed they him to tarry certain days.

Acts 19:5  When they heard [this], they were baptized in the name of the Lord Jesus.

Acts 22:16  And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.

Not one single time do you read of the Apostles repeating the words, "in the name of the Father, and of the Son and of the Holy Ghost."  But each and every time they baptized, they obeyed Jesus' command by speaking the NAME, "Jesus."

The issue of AUTHORITY is brought up when you speak to some people about the utterance of the NAME being important in baptism.  Some will say that the AUTHORITY is what is referred to and not the actual personal name by which one is known to others.  They say it is not a reference at all to the actual name "Jesus Christ" but rather the authority and power of God that is the actual issue.  This is a moot argument because you cannot separate the authority from the name of the individual holding the authority.  In fact, that is why the actual name of an individual, distinguishing them from all other people, is indeed a "name."  Authority and Name are inseparable.  Yes, authority is noted in the baptismal references when speaking of "in the name of."  But that is all the more reason the actual Name of Jesus Christ ought to be noted in invocation when a person is baptized to indicate that AUTHORITY and where it is centred.

Matt 28:18  And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth. 
Matt 28:19  Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:

Notice in the above verses that Jesus Christ initially says that all power (AUTHORITY) is given to Him.  And then He said, "Go ye therefore..."

This is very enlightening!!  He gives a command to baptize people based upon the truth of verse 18!  In other words, the reason we are to baptize in the Name of the Father and of the Son and of the Holy Ghost is found in verse 18.  What is the reason?  The reason we are to baptize is the fact that Jesus has been given all AUTHORITY in heaven and earth.  This incontrovertibly proves that Jesus was referring to His own personal authority and personal Name, "Jesus Christ," when He spoke the words of Matthew 28:19.

So, if Jesus indeed referred to HIS AUTHORITY He possessed, as described in verse 18, then it is no wonder that the Apostles obeyed that command by actually invoking the name of "Jesus Christ" whenever they baptized people as recorded throughout the book of Acts.  Yes, it was referring to authority.  But since Jesus said it was the authority given to Him, and since the only utterances we find in the Book of Acts during baptism included the NAME of "Jesus Christ," then we clearly see that the name must be invoked at water baptism, along with the understanding that this name indisputably points to His authority and power in heaven and earth.

Utterance was definitely referred to as we find out in Acts 22:16.

Acts 22:16  And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.

The term CALLING ON comes from the Greek word "epikaleomai" {ep-ee-kal-eh'-om-ahee} which refers to the practice of beginning a prayer by invoking the divine name.  Actual utterance is referred to by way of invocation during Baptism.

Many think that NAME ought not necessarily be uttered so long as the authority is understood.

Acts 16:18  And this did she many days. But Paul, being grieved, turned and said to the spirit, I command thee in the name of Jesus Christ to come out of her. And he came out the same hour.

Did Paul have to utter the name of Christ in invocation in order to cast out the devil?  I think so.

Colo 3:17  And whatsoever ye do in word or deed, do all in the name of the Lord Jesus, giving thanks to God and the Father by him.