"Should Contain" — a word or words (metatags) that are desired or possibly correct but not critical to finding the desired publication. This field is helpful if you are not sure what the correct metatags are.
For example: You can type Smith Jones to get results from authors with either of those surnames.
"Must Contain" — metatags that are necessary to finding the desired publication. This field is helpful if you are certain of key words in the publication you are seeking.
For example: If you know that Jones was the author of the publication, you can key in the name and see all publications that have Jones listed in them. If, on the other hand, you key in Jones and Smith, you will only receive information on publications that contain references to Jones and Smith.
Also note that the "Must Contain" field cancels out the "Should Contain" one. For example: If you key in "Must Contain" Jones and "Should Contain" Smith, you will receive information on all publications with Jones listed in them, regardless of whether or not Smith is, too.
"Must Not Contain" — metatags that are not associated with the desired publication and would in fact invalidate the search. This field is helpful if you are certain of key words that are not in the publication you are seeking.
For example: If you key in "Must Not Contain" Jones but "Must Contain" Smith, you will receive information on all publications with Smith listed in them that do not also include Jones.
Subject/Key Words — Among the features in ETS ReSEARCHER is the ability to search the database by subject through the use of key words assigned to each report. To use this feature look for the "Subject/Key Words" field on the ETS ReSEARCHER form. ETS also offers a listing of subjects, key words or phrases that commonly appear in ETS ReSEARCHER.