Breaking headlines

In headlines, do prepositions go at the end or at the beginning of the line? What about articles?

I’ve seen arguments for both. Some say phrases with prepositions can’t be broken because that would be against the unnatural flow. Others say a headline is better readable if each line makes sense on its own, or at least its beginning does.

Example (nevermind balancing lines, this is not the point here):

An Act to approve
the Constitution
of the United Nations
Educational, Scientific
and Cultural Organization

or

An Act to approve the
Constitution of the
United Nations Educational,
Scientific and Cultural Organization