More books

Lehmann - Proto-Indo-European Syntax
https://docs.google.com/file/d/0B2MQAxDmRLhuS1VqR0picGIwSVU/edit?usp=sharing

Lehmann - Proto-Indo-European Phonology
https://docs.google.com/file/d/0B2MQAxDmRLhuMWlTeUF2aXMtbUU/edit?usp=sharing

Lehmann - On Earlier Stages of the Indo-European Nominal Inflection
https://docs.google.com/file/d/0B2MQAxDmRLhuSlRILU1sYm5JaEk/edit?usp=sharing

Collinge - The Laws of Indo-European
https://docs.google.com/file/d/0B2MQAxDmRLhuQ3l0QlppVWQ4VWM/edit?usp=sharing

(This pdf is made by me personally, of images found on the Net. It means it is not searchable. However, it has bookmarked. Probably each IE researcher knows what Grimm's Law is - but not everyone knows what Zipf's Principle says. This is a good source of such information.)