Some times with in a sentence an article can be used more than once as per the following the rules.
a. When two or more than two nouns refer to the same person or thing, the article is used before the first. But when they refer to two persons or things, the article is placed before each.
b. When two or more adjectives qualify the same noun, the article is placed before the first.
c. In expressing, a comparison if two nouns refer to the same person or thing, the article is prefixed to the first noun only. But if they refer to different persons or things, the article must be put before each noun.
a. The secretary and the stenographer have come.
b. I bought a white and a red cow.
c. Our headmaster is a better administrator than a better teacher.