Perhaps you should try some spelling variations:
"tropico americanos de medicina interna ;" » "tropico americano de medicina interna ;", "tropico mexicano de medicina interna ;", "subtropico americano de medicina interna ;", "tropico americana de medicina interna ;"
"cronicas americano en medicina interna ;" » "cronicas americanas en medicina interna ;", "cronica mexicana en medicina interna ;", "tropico americano en medicina interna ;", "cronicas americana en medicina interna ;", "cronicas americano la medicina interna ;"

Try widening your search to All Fields.

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

• Performing a fuzzy search may retrieve terms with similar spellings: (("tropico americanos de medicina interna ;") or ("cronicas americano en medicina interna ;"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("tropico americanos de medicina interna ;") OR ("cronicas americano en medicina interna ;")).
• Removing quotes may allow a broader search: (( tropico americanos de medicina interna ; ) or ( cronicas americano en medicina interna ; )).
• Adding a wildcard symbol may retrieve word variants: (("tropico americanos de medicina interna ;") or ("cronicas americano en medicina interna ;"))*.