Perhaps you should try some spelling variations:
toc sach » doc sach, thuoc sach, nuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
hoc sach » hoc sinh, hoc cac, hoc anh
cau treo » cau theo, cau tren, cau triet
nang ma » tang ma, sang ma, nang cao
thuc va » thuc vat, thuc dan, thuc day
dan tai » van tai, dan thi, han tai
dan vat » dang vat, van vat, dan va
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: ((toc sach) OR (hoc sach)) ky nang ma hoi. hieu van nam thuc va ((dan tai) or (dan vat)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc sach)) ky nang ma hoi. hieu van nam thuc va ((dan tai) OR (dan vat)) cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) OR (hoc sach)) ky nang ma hoi. hieu van nam thuc va ((dan tai) or (dan vat)) cau treo".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) OR (hoc sach)) ky nang ma hoi. hieu van nam thuc va ((dan tai) or (dan vat)) cau treo*.