Mostly convention, but also compromise. You may like:<p><a href="http:&#x2F;&#x2F;research.microsoft.com&#x2F;en-us&#x2F;um&#x2F;people&#x2F;lamport&#x2F;pubs&#x2F;proof.pdf" rel="nofollow">http:&#x2F;&#x2F;research.microsoft.com&#x2F;en-us&#x2F;um&#x2F;people&#x2F;lamport&#x2F;pubs&#x2F;p...</a>