Perhaps you should try some spelling variations:
kham thong » khap thong, khau thong, pham thuong
khoa kham » kho khan, khoa than
dac khoa » da khoa, dai khoa, dau khoa
sach bai » sach dao, cac bai, sach xa
sach tri » sach tai, sach tren, sach truc
tu sach » thu sach, te sach, tu cach
su sach » so sach, vu sach
khoa he » hoa he, khoa hoc, khong he
ve cach » va cach, ve canh
ve cac » va cac, vien cac
bai le » ban le, tai le, bac le
le dac » le dan, le duc

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

• Performing a fuzzy search may retrieve terms with similar spellings: (( su sach tri ((ve cach) OR (ve cac)) khoa kham thong ) or ( tu sach bai le dac khoa he thong ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( su sach tri ((ve cach) OR (ve cac)) khoa kham thong ) OR ( tu sach bai le dac khoa he thong ))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( su sach tri ((ve cach) OR (ve cac)) khoa kham thong ) or ( tu sach bai le dac khoa he thong ))*".