Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
cam tuc » cam xuc, cam tu, nam thuc
vai cua » dai cua, hai cua, lai cua
tuc van » thuc van, truc van, tuc va
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
nang ma » tang ma, sang ma, nang cao
ve cam » ve cham, ve cac, va cam

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((nang ma) or (nang x)) hoi. hieu ve cam tuc van hanh ((vai cuu) OR (vai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang ma) OR (nang x)) hoi. hieu ve cam tuc van hanh ((vai cuu) OR (vai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((nang ma) or (nang x)) hoi. hieu ve cam tuc van hanh ((vai cuu) OR (vai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang ma) or (nang x)) hoi. hieu ve cam tuc van hanh ((vai cuu) OR (vai cua)) tre*.