In 1990, teaching and research assistants in the Graduate School of Arts and Sciences decided to organize a union, GESO, and affiliated with the federation. There were several strikes in the 1990s, including two successive one month walkouts by Locals 35 and 34, respectively, in the spring semester of 1996. The 1996 strike was concerned primarily with the issue of subcontracting. During the strike, Local 35 organized nearly 300 casual workers into its bargaining unit, but Yale inserted a loophole into the contract which gave it the ability to subcontract work in any new or renovated buildings, and then promptly began a campaign to renovate nearly all of its major buildings.