The paper probably meant that motional relaxation is absent in solids. J(0), however, causes line-broadening, often expressed as the second moment. A good discussion cam be found in chapter 3 of C.P.Slichter's book "Principles of Magnetic Resonance".

Dear Juan - the author of the papper you read must have expressed him or herself rather badly,. Dr Post´s  comment is to the point - and Slichters book is a good source.

Best

Sture