Perhaps you should try some spelling variations:
thu sach » thuat sach, thuoc sach, thu hoach
nang cam » nang cham, nang cao, nang cap
tinh dan » trinh dan, tinh da, binh dan
truc va » thuc va, trung va
nang ma » tang ma, sang ma, nang cao
tu sach » su sach, te sach, tu cach
ma hoi » mai hoi, xa hoi, ma hoa
ca tre » ca tren, cua tre, ca tru

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