Perhaps you should try some spelling variations:
"phat trien khai hoc" » "phat trien nha hoc", "phat trien thai hoc", "phat trien khi hoc", "phat trien khai thac", "phan trien khai hoc", "nhat trien khai hoc"
"phap trien khai hoc" » "phap trien nha hoc", "phap truyen khai hoc", "phap tieng khai hoc", "phap tiep khai hoc", "phap trien thai hoc", "phap trien khi hoc", "phap trien khai thac"
"pham trien khoa hoc" » "pham tien khoa hoc", "pham tren khoa hoc", "pham lien khoa hoc", "pham trien nha hoc", "pham trien hoat hoc", "pham vien khoa hoc", "pham trien hoa hoc"

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("phat trien khai hoc") OR ("phap trien khai hoc"))) or ("pham trien khoa hoc"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("phat trien khai hoc") OR ("phap trien khai hoc"))) OR ("pham trien khoa hoc")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"phat trien khai hoc\") OR (\"phap trien khai hoc\"))) or (\"pham trien khoa hoc\"))".
• Removing quotes may allow a broader search: (((( phat trien khai hoc ) OR ( phap trien khai hoc ))) or ( pham trien khoa hoc )).
• Adding a wildcard symbol may retrieve word variants: (((("phat trien khai hoc") OR ("phap trien khai hoc"))) or ("pham trien khoa hoc"))*.