We go together like ...
I've been seeing this error enough lately that I figure it's worth a post.
When listing a series of things, you don't have to repeat the article if it goes with every noun in the series: She found a cat, dog, parakeet and walrus in her bedroom.
But when the article doesn't work across the board, every noun needs to get its own.
WRONG: The project will include an atrium, garden, swings and fountain.
RIGHT: The project will include an atrium, a garden, swings and a fountain.
An does not go with garden and can therefore not be shared by all the items in the series. You have to make everything parallel.
And watch out especially for a and an switches. Those can sneak up on you.