Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van chat » cao chat
duc manh » suc manh, duc anh, duc minh
hanh tri » thanh tri, hanh tai, hanh trinh
ky lang » ky dang, ky tang, tay lang
duc van » duc va, duc tan, duc phan
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 ((ky lang) or (ky nang)) cao hieu. hieu van chat ((duc van) OR (duc manh)) hanh tri cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ((ky lang) OR (ky nang)) cao hieu. hieu van chat ((duc van) OR (duc manh)) hanh tri cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ((ky lang) or (ky nang)) cao hieu. hieu van chat ((duc van) OR (duc manh)) hanh tri cua te".
• Adding a wildcard symbol may retrieve word variants: toc sach ((ky lang) or (ky nang)) cao hieu. hieu van chat ((duc van) OR (duc manh)) hanh tri cua te*.