original: Several versions of the protocol exist; versions 1 3 occurred only internally at MIT.
simplifications: Several versions of the protocol exist including versions 1 and 3 which occurred only internally at MIT. Several versions of the aggreement exist; versions 1 and 3 happened only inside MIT. There are a few versions of the protocol; versions 1 3 is only at MIT. Several versions of the protocol exist. 1 - 3 happened only at MIT. Several versions of the protocol exist.  Versions 1 through 3 occurred only internally at MIT. There are several versions of the protocol. Versions 1 3 occurred only within MIT. Several versions of the protocol exist. Versions 1 3 were only internally at MIT. Several versions of the protocol exist. Version 1 and 3 were never public. The protocol has several versions but 1 3 was internal at MIT. There's many versions of the protocol; versions 1 3 have only occurred internally at MIT.