You are not supposed to believe in book / file. You are supposed to believe in recipient and sender of file / book. Pl.never believe in subject book. Believe in writer and student of subject book. Because purpose of studies is to change title of subject book "through analytical/development ability". All NCERT books are analytical-oriented. Pl.remember.

ఫైళ్లను నమ్మరాదు .
ఫైళ్లను గౌరవించి ఆ ఫైల్ వ్రాసిపంపిన వారిని మరియు ఆ ఫైల్ అందుకున్న వారిని నమ్మాలి .