Perhaps you should try some spelling variations:
programming samples » programming examples, programming styles, programming camps
samples microarray » sample microarray, simple microarray, series microarray
external persons » external versus, external periodic, external perceptions
microarray chips » microarray chip, microarrays chip, microarray cross
external python » external pathogen, external action

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: ((external python) OR (external persons)) programming samples microarray chips~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((external python) OR (external persons)) programming samples microarray chips".
• Adding a wildcard symbol may retrieve word variants: ((external python) OR (external persons)) programming samples microarray chips*.