Whenever the planning commission in cities of the first class having a population of more than sixty thousand (60,000) have filed with the governing body a master plan for the physical development of the city and land outside the city, which plan will require a number of years to execute, and such master plan is approved by the governing body of such city, such city is hereby authorized to issue general obligation bonds in an amount sufficient to carry out such master plan: Provided, No such bonds shall be issued until authorized in the manner provided in Kan. Stat. Ann. § 13-1116 by a vote of the electors of such city.