=head1 NAME
BN_add, BN_sub, BN_mul, BN_div, BN_sqr, BN_mod, BN_mod_mul, BN_exp,
-BN_mod_exp, BN_gcd - Arithmetic operations on BIGNUMs
+BN_mod_exp, BN_gcd - arithmetic operations on BIGNUMs
=head1 SYNOPSIS
BN_sub() subtracts B<b> from B<a> and places the result in B<r> (C<r=a-b>).
BN_mul() multiplies B<a> and B<b> and places the result in B<r> (C<r=a*b>).
-For multiplication by powers of 2, use BN_lshift(3).
+B<r> may be the same B<BIGNUM> as B<a> or B<b>.
+For multiplication by powers of 2, use L<BN_lshift(3)|BN_lshift(3)>.
BN_div() divides B<a> by B<d> and places the result in B<dv> and the
remainder in B<rem> (C<dv=a/d, rem=a%d>). Either of B<dv> and B<rem> may