Constructing a Steiner Triple System of Order 19 Using the Doubling Construction

[pupeye11]

Homework Statement

Use the doubling construction to construct a Steiner Triple System of order 19. (Exhibit the blocks.)

The Attempt at a Solution

My first question is, what is a doubling construction? I can't find it in my book or on the internet.

 

[pupeye11]

Alright well I found out a doubling construction is just the fact that if an STS of order v, STS(v) exists then so does an STS(2v+1). So that means that my STS(19) is the same as a STS(39). Not sure what to do from there though...