 Complete the following phrase:  It appears that the Treaty of Taif was renewed as scheduled in 1974, though the details of the renewal remained uncertain, largely as Yemen did not wish to be seen to be renouncing its traditional claim to Asir, Jizan and Najran. Following the unification of Yemen in 1990, the upcoming need to renew the Treaty of Taif, and also the discovery of oil in the border region, prompted the reinstigation of boundary negotiations in 1992. Negotiations stalled due to the 