Perhaps you should try some spelling variations:
doan thi » dan thi, doanh tai, hoang thi
toc sach » hoc sach, doc sach, thuoc sach
cau tren » cu tren, dau tren, ca tren
tu sach » thu sach, su sach, te sach
cau duc » cao duc, cau luc, cau truc
chu duc » thu duc, chua duoc, cuu duoc
va doan » va doanh, van doan, va dan
thi cau » thi chau, thi cu, thi cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((tu sach) or (toc sach)) ky nang x ho. hieu qua ((cau duc) OR (chu duc)) va doan thi cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((tu sach) OR (toc sach)) ky nang x ho. hieu qua ((cau duc) OR (chu duc)) va doan thi cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((tu sach) or (toc sach)) ky nang x ho. hieu qua ((cau duc) OR (chu duc)) va doan thi cau tren".
• Adding a wildcard symbol may retrieve word variants: ((tu sach) or (toc sach)) ky nang x ho. hieu qua ((cau duc) OR (chu duc)) va doan thi cau tren*.