Perhaps you should try some spelling variations:
nam thuoc » nam thuc, nam thu, nha thuoc
doc sach » hoc sach, toc sach, nuoc sach
dau tren » dau tien, dau tieng, dau trong
cau tren » cu tren, ca tren, cau treo
thuoc va » thuc va, thuoc ma, thuong va
dat tren » dat trong, dua tren
hieu va » lieu va, hieu qua
sach ty » sach y, sach tu, sach thu
dan vai » dan va, dan tai, dan vat
lang xa » lang ha, dang xay, lang van
ty lang » tay lang, ty xang, ty hang
va nam » van nam, ha nam, va nay
va dan » ca dan, va dao, va dau

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 lang xa hoi. hieu va nam thuoc va dan vai ((cau tren) or (((dau tren) OR (dat tren))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc sach ty lang xa hoi. hieu va nam thuoc va dan vai ((cau tren) OR (((dau tren) OR (dat tren)))).
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc sach ty lang xa hoi. hieu va nam thuoc va dan vai ((cau tren) or (((dau tren) OR (dat tren))))".
• Adding a wildcard symbol may retrieve word variants: doc sach ty lang xa hoi. hieu va nam thuoc va dan vai ((cau tren) or (((dau tren) OR (dat tren))))*.