In a professional paper, you should be synthesizing information not just summarizing each source. Instead of summarizing, you should look for ways in which your various articles agree/disagree and what unique points or insights appear in each so that you can combine (synthesize) the information to write much more robust paragraphs. If you only have one article which addresses a particular portion of your paper, you may need to find additional sources which discuss that part of the topic.
To view an example of synthesizing, open the sample article link below and look for the section labeled background. (Note that this paper does not use APA formatting). Notice how the authors often cite more than one source (this shows up as places where more than one number follows a sentence, the numbers refer to the position of the reference in the reference list). When the authors list more than one source after a sentence, they are paraphrasing a concept which appears in more than one source and citing each source they used for their paraphrase. Reading the background or literature reviews of articles from nursing journals can help you develop a sense of how authors use synthesizing (effectively or ineffectively!).
To learn more about synthesizing and how to effectively synthesize, open up the link labeled "Instructions for Synthesis Matrix". Read through the handout to see how to organize the information from multiple sources and then synthesize that information. The last link is for a blank synthesis matrix if you would like to use one for your literature review..