Perhaps you should try some spelling variations:
trinh cuu » trinh cau, trinh cua, trinh chu
toc sach » hoc sach, doc sach, thuoc sach
sach ky » sac ky, sach y, sach ty
tri cuu » tri cua, tra cuu, troi cua
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
tuc va » thuc va, truc va, tuc xa
loc va » hoc va, luc va
va cam » va cham, va cac, va cao
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 ky nang ma hoi. hieu va cam ((tuc va) or (loc va)) hanh ((tri cuu) OR (trinh cuu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky nang ma hoi. hieu va cam ((tuc va) OR (loc va)) hanh ((tri cuu) OR (trinh cuu)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky nang ma hoi. hieu va cam ((tuc va) or (loc va)) hanh ((tri cuu) OR (trinh cuu)) tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky nang ma hoi. hieu va cam ((tuc va) or (loc va)) hanh ((tri cuu) OR (trinh cuu)) tre*.