Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
cua tec » cua tuc, cua toc, cua viec
luc van » luoc van, luu van, duc van
cac luc » cau luc, coc luc, cac nuoc
hieu ve » hieu va, hieu van
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
sach v » sach va, sach y, sach 2
ve cac » va cac, vien cac
cua te » cua tu

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 v ((nang ma) or (sang ma)) hoi. hieu ve cac luc van hanh vi ((cua tec) or (cua te))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach v ((nang ma) OR (sang ma)) hoi. hieu ve cac luc van hanh vi ((cua tec) OR (cua te)).
• Adding a wildcard symbol may retrieve word variants: toc sach v ((nang ma) or (sang ma)) hoi. hieu ve cac luc van hanh vi ((cua tec) or (cua te))*.