Will look at it. More speciifically, I am looking at ways to estimate the likelihood function of the individual responses to closed-ended contingent valuation question. I contacted the authors, but have not been successful getting a reply back so far.
At the University of Barcelona is Professor Pere Riera who has fairly developed on environmental valuation. You can Google it.
I wrote my doctoral thesis at the Technical University of Madrid "Development of a new method of environmental assessment" but is written in Spanish. You can download it from my profile Research Gate if you need it.