Perhaps you should try some spelling variations:
dung tren » dung trong, dung trung
hanh truc » hang truc, nhanh thuc, hanh thuoc
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
truc va » thuc va, thuc vat, trung va
sach ty » sach y, sach tu, sach thu
vu sach » vu bach, su sach, vu khach
ty nang » ky nang, ty xang, ty hang
cuu tre » cua tre, cau tren, cau treo
ma hoi » mai hoi, ma hoa, me hoi
va dan » ca dan, va dao, va dau
dan vi » doan vi, don vi, dan va

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ty nang ((ma hoi) or (xa hoi)). hieu van hanh truc va dan vi ((dung tren) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ty nang ((ma hoi) OR (xa hoi)). hieu van hanh truc va dan vi ((dung tren) OR (cuu tre)).
• Adding a wildcard symbol may retrieve word variants: vu sach ty nang ((ma hoi) or (xa hoi)). hieu van hanh truc va dan vi ((dung tren) or (cuu tre))*.