It's a public letter. For instance, one important paper is the paper from Lester et al., 2009, in Marine Ecology Progress Series. It really showed the impact of no take. It showed that no-take zones provided more benefits than zones of lower protection.
In terms of science, one paper we refer to a lot is by Graham Edgar and other authors, in 2014, in Nature. Nature is one of the best journals we have in science. They did a larger analysis of a number of MPAs in different regions, in different contexts, and tried to see what criteria explained why some work and some don't work. They showed that the larger the MPA and the higher the level of protection and all that, the better it works. This is all supported by statistics. It's top, peer-reviewed research.
There are actually 20 or 30 papers that prove that MPAs work, but my caveat is that they only work if they are designed properly. They only work if the science is behind this to assess how big they have to be, where they have to be, and at what level of protection. That's one thing that we are concerned about, that sometimes with the trade-offs we make the resulting MPA does not necessarily work.