http://ice.he.net/~freepnet/fbifiles/100-HQ-448092/Section%2015/Section%2015.pdf
See, among others, page 25 (top):
"... That on April Four, One Nine Seven Two, a representative of the North Vietnamese government at the Paris peace talks telephoned the "movement" in the United States to be ready to take action, presumably demonstrations, to counter expected escalation of bombing by American air forces in South Vietnam as a result of the increased military action of north Vietnamese forces in Quang Tri province, South Vietnam."
Damn