Lode Angle History?

All,

In my research, I have been using the Lode angle of the stress tensor in a fracture model. Consequently, I've been reading up on the Lode angle and have found that just about each publication defines their own Lode angle that is slightly different from everyone else. So, I've searched around to find out the history of the Lode angle, but have come up empty-handed. I would imagine that the Lode angle is named after some Mr. Lode, but I cannot even find his first name. Do any of you know where, when, or who came up with the idea of the Lode angle? Particularly, I would like to get a copy of the first publication, if you happen to have one or know where one might be.

Thanks,

Scot Swan