1 Where the books had been printed first.2.if the books had been printed first in the 15th century.2. 1.What printers in three countries had started doing at the same time. 2.If printers had started printing books in three countries at the same time.3.1. Where anyone could read books those days2.If anyone could read books on CDs those days.4. 1.What Columbus had discovered five centuries before.2. If Columbus had discovered Аmerica five centuries before.5.1.What the Internet provided us with.2. If the Internet provided us with access to any library all over the world.6.1.When people living in one part of the world hadn't known much about the life of people in their neighbouring countries.2. If people living in one part of the world had known much about the life of people in their neighbouring countries not long before.