Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
van thanh » ban thanh, van tuan
thu sach » tu sach, thuat sach, thuoc sach
dua tren » dung tren
nang ma » tang ma, nang cao, mang may
sach ky » sac ky, sach y, sach ty
luu van » cuu van, luan van, luu hanh
sang ma » tang ma, sang tao, mang may
vai dua » dai dua, vai cua
ve cac » va cac, vien cac
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: thu sach ky ((sang ma) OR (nang ma)) hoi. hieu ((ve cau) or (ve cac)) luu van thanh vai dua tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((sang ma) OR (nang ma)) hoi. hieu ((ve cau) OR (ve cac)) luu van thanh vai dua tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky ((sang ma) OR (nang ma)) hoi. hieu ((ve cau) or (ve cac)) luu van thanh vai dua tren".
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((sang ma) OR (nang ma)) hoi. hieu ((ve cau) or (ve cac)) luu van thanh vai dua tren*.