JSTOR is an excellent source for articles. It doesn't include articles published in the last couple of years, so remember to check other sources for themost recent work.
The Advanced Search enables you to search several fields for your keyword, including full text. In a database as large as this one you may find too many occurences of your term and find it useful to use the item title field. You may also narrow your results to 'Articles' to avoid finding book reviews.
When you find an article you may wish to determine if the article is peer reviewed, scholarly or popular. While you would not use a popular article for your research section you may find images in popular sources to use for your Google Earth Project.
Ulrich's Periodicals Directory will identify the type of publication you are using.
Look up the title of the publication, click on the matching entry for the title to display the description of the publication. Refereed is the term for peer reviewed.
This box will allow you to search the Summon database. Just remember it is very broad and you will need to refine your results.
If you have any concerns about the type of article you should look up the publication in the Ulrich's Periodical Directory (see the box on this page).