Perhaps you should try some spelling variations:
occasional letters » occasional writer, occasional prayers, occasional papers
occasional notices » occasionally noticed, occasional offices, occasional copies
occasional letter » occasional writer, occasional verse
occasional notess » occasional poems, occasion notes, occasional distress

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (( occasional letters; occasional letter ) OR ( ((occasional notess) OR (occasional notices)); occasional notes )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( occasional letters; occasional letter ) or ( ((occasional notess) OR (occasional notices)); occasional notes ))".
• Adding a wildcard symbol may retrieve word variants: (( occasional letters; occasional letter ) or ( ((occasional notess) OR (occasional notices)); occasional notes ))*.