Perhaps you should try some spelling variations:
thach duc » thach thuc, than duc, thinh duc
toc sach » hoc sach, doc sach, thuoc sach
va thach » va thanh, vay khach, mai thach
va hanh » van hanh, va thanh, va danh
hieu va » lieu va, hieu qua
vu nang » vuc nang, vu dang, v nang
va nang » van nang, da nang, cam nang
di cua » dai cua, doi cua, do cua
de cua » le cua, te cua, dieu cua

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 ((va nang) or (vu nang)) xa hoi. hieu va thach duc va hanh ((di cua) OR (de cua)) te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((va nang) OR (vu nang)) xa hoi. hieu va thach duc va hanh ((di cua) OR (de cua)) te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((va nang) or (vu nang)) xa hoi. hieu va thach duc va hanh ((di cua) OR (de cua)) te".
• Adding a wildcard symbol may retrieve word variants: toc sach ((va nang) or (vu nang)) xa hoi. hieu va thach duc va hanh ((di cua) OR (de cua)) te*.