Perhaps you should try some spelling variations:
doc sach » hoc sach, toc sach, nuoc sach
vien cac » vien bach, vien dai, vien da
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang ma » tang ma, sang ma, nang cao
ve cac » va cac
va dau » va dao
dau ve » dap ve
ve cau » ke cau, va cau, le cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc sach ty nang ma hoa. hieu ((ve cac) or (vien cac)) nuoc va dau ve cau tao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty nang ma hoa. hieu ((ve cac) OR (vien cac)) nuoc va dau ve cau tao.
• Adding a wildcard symbol may retrieve word variants: doc sach ty nang ma hoa. hieu ((ve cac) or (vien cac)) nuoc va dau ve cau tao*.