Perhaps you should try some spelling variations:
sach trien » sach tien, sach thieu, cach thien
sach tren » sach tien, sach tranh
khat khoa » khuan khoa, pham khoa, vat khoa
doc sach » hoc sach, toc sach, nuoc sach
sach xin » sach kinh, sach tien, sach xa
nhi khoa » noi khoa, tai khoa, anh khoa
khoa hoc » hoa hoc
xin nhi » vien nhi

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 xin nhi khoa hoc ) or ( su ((sach trien) OR (sach tren)) khat khoa hoc ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( doc sach xin nhi khoa hoc ) OR ( su ((sach trien) OR (sach tren)) khat khoa hoc )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( doc sach xin nhi khoa hoc ) or ( su ((sach trien) OR (sach tren)) khat khoa hoc ))".
• Adding a wildcard symbol may retrieve word variants: (( doc sach xin nhi khoa hoc ) or ( su ((sach trien) OR (sach tren)) khat khoa hoc ))*.