 Systematic Replication. It goes right along well with Direct Replication. It speaks to our ability of our field to create findings that generalize, right? But more importantly, with a Systematic Replication, what we're trying to do is kind of find the extent to which something functions, right? So I've always used an example of Direct Instruction. So with Systematic Replication, what we can do is we take an experiment, but then we tweak it, we vary something. One thing and we vary it just a wee bit to see if we still get the same findings, the same results with that slight change. Maybe it's a different type of subject, participant, right? So maybe it's a different type of slight change to the intervention with one less hour of work or two less hours of work or something like that. Whatever it is, it's some small change to the experiment to see if you still get those same findings that you got from the original study. So again, back to the Direct Instruction thing. So we say, hey, Direct Instruction works great for teaching people to read. Let's see if we can do it to teach someone some math skills. Now let's see if we can do it to teach someone science. That's the Systematic Replication piece. So the combination of Systematic and Direct Replication really helps our science build on a solid foundation. And that is the core of single-subject research, are those two pieces, along with the internal validity stuff that we'll talk about it another time. Bye!