Perhaps you should try some spelling variations:
cham duc » cham soc, phan duc, cham cuu
van hanh » van thanh, ban hanh, van anh
sach ty » sach y, sach tu, sach thu
hanh vu » hanh vi, hanh va, hanh tu
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
ty nang » ky nang, ty xang, ty hang
ma hoi » mai hoi, xa hoi, ma hoa
vu va » vu van, tu va, su va
thiet » thieu

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 ty nang ma hoi. hieu ve ((cham duc) or (((pham duy) or (pham duc)))) van hanh vu va thiet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ty nang ma hoi. hieu ve ((cham duc) OR (((pham duy) OR (pham duc)))) van hanh vu va thiet.
• Adding a wildcard symbol may retrieve word variants: tu sach ty nang ma hoi. hieu ve ((cham duc) or (((pham duy) or (pham duc)))) van hanh vu va thiet*.