Perhaps you should try some spelling variations:
"copulas mathematical computer programs." » "copulas mathematics computer programs.", "computers mathematical computer programs.", "costs mathematical computer programs.", "comicas matematicas computer programs.", "copulas mathematical computer programas.", "copulas mathematical computer programa."
"basicas matematicas computer programmers." » "basicas mathematics computer programmers.", "basicas matematicas como programmers.", "basicas matematicas comics programmers.", "basicas matematicas computer programming.", "basicas matematicas computers programming.", "basicas matematicas computer program.", "comicas matematicas computer programmers.", "benditas matematicas computer programmers.", "fisica matematica computer programmers."

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: (("basicas matematicas computer programmers.") OR ("copulas mathematical computer programs."))~.
• Removing quotes may allow a broader search: (( basicas matematicas computer programmers. ) or ( copulas mathematical computer programs. ))~.
• Adding a wildcard symbol may retrieve word variants: (("basicas matematicas computer programmers.") or ("copulas mathematical computer programs."))*.