Citation in text. Please ensure that every reference cited in the text is also present in the reference list (and vice versa). Do not cite references in the abstract. The citation of a reference as 'in press' indicates that the item has been accepted for publication. Unpublished results and personal communications should not be included in the reference list but may be mentioned in the text.
Reference list. Indicate references by consecutive superscript Arabic numerals in the order in which they appear in the text. The numerals are to be used outside periods and commas; inside colons and semicolons. For further detail and examples, please refer to the APA Manual of Style, A Guide for Authors and Editors, 6th Edition. Sample reference to a journal publication:

Van der Geer, J., Hanraads, J. A. J., & Lupton, R. A. (2010).  The art of writing a scientific article. J Sci Commun, 4(163), 51-59.

Sample reference to a book:
Strunk, W. Jr., &  White, E. B. (2000). The elements of style (4th ed.). New York, NY: Longman.

Sample reference to a chapter in an edited book:

Mettam, G. R., & Adams, L. B. (2009).  How to prepare an electronic version of your article. In: Jones, B. S., & Smith, R. Z., (eds.), Introduction to the electronic age. New York, NY: E-Publishing Inc, 281-304.