Create spectroscopy-letters

I've started working from the applied spectroscopy style as mentioned in the summary. 
There are still a few issues, but at least it seems to be compliant to 100% with journal references
Issue: a comma after the date still appears in the book references and I didn't know how to remove it. Probably it works with conditionals...)
This one is very tricky. I'm a total newbie you know... What to do? I want a , after the date in a journal citation, but not after the date of a Book citation. 
Somehow for now the result serves my purpose quite well although it's not perfect. But I can edit the errors manually. Of course if we find the solution it's better for future users...