Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh tai » thanh tai, hang tai, han tai
dan hanh » dang hanh, dan khanh, dan thanh
cam thuc » am thuc, nam thuc, can thuc
sua viet » su viet, cua viet, lua viet
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
cam thu » nam thu, cac thu, ca thu
vu sach » vu bach, su sach, vu khach
tai sua » dai sua, tai su, tai cua
ma hoi » mai hoi, xa hoi, ma hoa

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 (vu sach)) ky nang ma hoi. hieu va ((cam thuc) OR (cam thu)) dan hanh tai sua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (vu sach)) ky nang ma hoi. hieu va ((cam thuc) OR (cam thu)) dan hanh tai sua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (vu sach)) ky nang ma hoi. hieu va ((cam thuc) OR (cam thu)) dan hanh tai sua viet".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (vu sach)) ky nang ma hoi. hieu va ((cam thuc) OR (cam thu)) dan hanh tai sua viet*.