Perhaps you should try some spelling variations:
tranh khat » tranh chap, tran nhat, trinh khai
sach tranh » canh tranh
trinh han » trinh quan
khat khoa » khuan khoa, pham khoa, vat khoa
tinh hai » tinh thai, tinh chat, thanh hai
khoa hoc » hoa hoc
tu sach » thu sach, su sach, te sach
tu bac » tu ban, tu cac, tu bat

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( tu bac ((tinh hai) OR (trinh han)) khoa hoc ) or ( tu sach tranh khat khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( tu bac ((tinh hai) OR (trinh han)) khoa hoc ) OR ( tu sach tranh khat khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( tu bac ((tinh hai) OR (trinh han)) khoa hoc ) or ( tu sach tranh khat khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( tu bac ((tinh hai) OR (trinh han)) khoa hoc ) or ( tu sach tranh khat khoa hoc ))*.