Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van nham » van nhan, van tham, van pham
vat danh » va danh, van danh, luat danh
danh sai » dung sai, danh bat, danh dau
cau tren » cu tren, dau tren, ca tren
hoc cac » hoc cao
ky lang » ky nang, ky dang, ky tang
lang xa » lang ha, dang xay, lang van
sai cau » lai chau, mai chau, hai chau

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) or (hoc cac)) ky lang xa hoi. hieu ((van nham) OR (van nam)) thuc vat danh sai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (hoc cac)) ky lang xa hoi. hieu ((van nham) OR (van nam)) thuc vat danh sai cau tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((toc sach) or (hoc cac)) ky lang xa hoi. hieu ((van nham) OR (van nam)) thuc vat danh sai cau tren".
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (hoc cac)) ky lang xa hoi. hieu ((van nham) OR (van nam)) thuc vat danh sai cau tren*.