Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
tai duc » tai cuc, mai duc, tai du
va hanh » van hanh, va thanh, va danh
cac dac » cac dan, cac dai, cac bac
cac tac » cac toc, cac bac, cac tai
duc tre » duoc tren, duc tien
hieu ve » hieu va, hieu van
dang ma » dang mau, dang mam, dang mat
ky dang » ky nang, ky danh
su sach » so sach, vu sach

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) or (su sach)) ky dang ma hoa. hieu ve ((cac tac) OR (cac dac)) va hanh tai duc tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (su sach)) ky dang ma hoa. hieu ve ((cac tac) OR (cac dac)) va hanh tai duc tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (su sach)) ky dang ma hoa. hieu ve ((cac tac) OR (cac dac)) va hanh tai duc tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (su sach)) ky dang ma hoa. hieu ve ((cac tac) OR (cac dac)) va hanh tai duc tre*.