Code table TCVN 3 is often used in school materials.
Unicode encoding is popular, it is quite easy to read documents written in mobile Unicode, other encodings such as TCVN, VNI cannot be read on IOS and Android , sometimes we get an attachment is written in these encodings, the reading of these documents will be a lot of trouble, before if you encounter these documents, you must turn on the laptop to open, but now we have How to read this stubborn document right on your mobile.
First you have to install Smart office 2 (price 9.51 USD ) on Play Store, then you can download your font set here (you can add the font to the path fontViet.zip/system/fonts) .
Finally, use Smart office 2 to test the office files written in VNI, TCVN3 encodings to check the results (here I have some office files for you to test).
This way has some deficiencies but it is also the best way to read VNI and TCVN3 fonts on Android today.
Good luck!