Perhaps you should try some spelling variations:
"newsvendor problemas del" » "newsvendor problemas de", "newsvendor problemas con"
"newsvendor problemas en" » "newsvendor problemas de"
"newsvendor problema del" » "newsvendor problema de", "newsvendor problema 18", "newsvendor problema 20"
"newsvendor problem del" » "newsvendor problem de", "newsvendor problem model", "newsvendor problema de"

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: (((("newsvendor problemas del") OR ("newsvendor problemas en"))) or ((("newsvendor problema del") or ("newsvendor problem del"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("newsvendor problemas del") OR ("newsvendor problemas en"))) OR ((("newsvendor problema del") OR ("newsvendor problem del")))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"newsvendor problemas del\") OR (\"newsvendor problemas en\"))) or (((\"newsvendor problema del\") or (\"newsvendor problem del\"))))".
• Removing quotes may allow a broader search: (((( newsvendor problemas del ) OR ( newsvendor problemas en ))) or ((( newsvendor problema del ) or ( newsvendor problem del )))).
• Adding a wildcard symbol may retrieve word variants: (((("newsvendor problemas del") OR ("newsvendor problemas en"))) or ((("newsvendor problema del") or ("newsvendor problem del"))))*.