Perhaps you should try some spelling variations:
"trinh dan quang luan bien soan" » "trinh dan quan luan bien soan", "trinh dan quang tuan bien soan", "trinh dan quang uan bien soan", "trinh han quang luan bien soan", "trinh san quang luan bien soan", "trinh da quang luan bien soan", "trinh dang quang luan bien soan", "trinh doan quang luan bien soan", "trinh van quang luan bien soan", "trinh dan quang luan lien soan", "trinh dan quang xuan bien soan", "trinh dan quang luong bien soan", "trinh dan quang luan bien so"
"trinh dung luan van kien hoa" » "trinh dung luan van tien hoa", "trinh dung luan van hien hoa", "trinh dung luan van chien hoa", "trinh dung luan van dien hoa", "trinh dung luan van kien ha"

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• Performing a fuzzy search may retrieve terms with similar spellings: (("trinh dung luan van kien hoa") or ("trinh dan quang luan bien soan"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("trinh dung luan van kien hoa") OR ("trinh dan quang luan bien soan")).
• Removing quotes may allow a broader search: (( trinh dung luan van kien hoa ) or ( trinh dan quang luan bien soan )).
• Adding a wildcard symbol may retrieve word variants: (("trinh dung luan van kien hoa") or ("trinh dan quang luan bien soan"))*.