=head1 GUARANTEES
-To ensure price source prices are comprehensible and reproucible, some
+To ensure price source prices are comprehensible and reproducible, some
invariants are guaranteed:
=over 4
=item *
-Composing price sources are disallowed for clarity, but all price sources need
+Composing price sources is disallowed for clarity, but all price sources need
to be aware of units. This is madness.
=back