Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
cau treo » cau tren, cau triet, cau trieu
cau theo » cau thi, cau tao
hieu va » lieu va, hieu qua
lang ha » long ha
sach ky » sac ky, sach y, sach ty
dan vai » dan va, dan tai, dan vat
ky lang » ky nang, ky dang, ky tang
ha hoi » hoa hoi, ha noi, xa hoi
va nam » van nam, ha nam, va nay

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 ky lang ha hoi. hieu va nam ((thuc vat) or (hoc dan)) dan vai ((cau treo) OR (cau theo))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang ha hoi. hieu va nam ((thuc vat) OR (hoc dan)) dan vai ((cau treo) OR (cau theo)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang ha hoi. hieu va nam ((thuc vat) or (hoc dan)) dan vai ((cau treo) OR (cau theo))".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang ha hoi. hieu va nam ((thuc vat) or (hoc dan)) dan vai ((cau treo) OR (cau theo))*.