<a href="https://arxiv.org/abs/0903.0340" title="arxiv link">Baez' article</a>, the <a href="https://golem.ph.utexas.edu/category/2009/02/new_structures_for_physics_iii.html" title="n-category cafe">discussion</a> and <a href="http://de.arxiv.org/abs/0904.4921" title="arxiv link">Manin's article</a> are perhaps interesting for you.