The Nitrogen Fix by Hal Clement 1981 Ace Paperback

The Nitrogen Fix - Paperback, by Hal Clement - Acceptable

Nitrogen Fix - Paperback, by Clement Hal - Acceptable

The Nitrogen Fix - Hal Clement (Harry Stubbs) - Mass Market 1981

The Nitrogen Fix by Hal Clement - Vintage Sci-Fi Paperback Book

Iceworld 1973 Paperback by Hal Clement

Vintage 1981 Del Rey Book Paperback Novel Close to Critical by Hal Clement