Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
bo sach » co sach, hoc sach
cau duc » cao duc, cau luc, chu duc
vai cua » dai cua, hai cua, lai cua
duc van » duc va, duc tan, duc manh
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, kho tang
ky lang » ky nang, ky dang, tay lang
de cua » le cua, te cua, dieu cua
va cau » van cau, va cac, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: bo sach ((ky lang) OR (ky tang)) xa hoi. hieu va cau duc van hanh ((de cua) or (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: bo sach ((ky lang) OR (ky tang)) xa hoi. hieu va cau duc van hanh ((de cua) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "bo sach ((ky lang) OR (ky tang)) xa hoi. hieu va cau duc van hanh ((de cua) or (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: bo sach ((ky lang) OR (ky tang)) xa hoi. hieu va cau duc van hanh ((de cua) or (vai cua)) tre*.