The intersection of mathematics education and history is a special place for Ken Clements and Nerida Ellerton.

That’s where they found new insight into a teenage Abraham Lincoln’s arithmetic skills, by connecting the dots on two pages of Abe’s 1825 math workbook. And it’s where they found each other.

Clements and Ellerton, professors in Illinois State’s Department of Mathematics, made headlines last week with their Lincoln announcement. But that’s only the latest achievement for this amazing partnership, which stretches back 28 years, the last eight as husband and wife. Together, the two Australians have studied the history of math education in the U.S. for years—literally writing the book on it.

So it’s fitting that the researchers who added new pages to—and subsequently reordered—what’s considered the oldest manuscript prepared by Lincoln would work at a University that Lincoln himself had a hand in founding, just up Interstate 55 from his presidential museum in Springfield. They appreciate the new pages not just because they’re Lincoln’s—but because they’re about math.

“We were just well placed to recognize and then follow it through and write about it,” Ellerton said. “It was pure chance that we found it, but then we had to make that link because it wasn’t known.”

Their partnership began in 1985 at Deakin University near Melbourne, when Ellerton served on the search committee that hired Clements. They collaborated often back then, hunched over the same computer together writing academic articles about their shared passion—mathematics education. (In the past 28 years, they’ve published more than 100 articles and several books together.)

After Ellerton’s first husband, David, died in 2001, she traveled to the U.S. and got a job at Illinois State. Then in 2005, the longtime friends who shared so much already but were on their own, decided to get married. That year, Clements got a job in Illinois State’s Department of Mathematics too.

They live in an old house together in Bloomington, and as you can imagine, they like to drink coffee together and talk shop. Because they often publish together, it feels very natural to bounce ideas off one another, Ellerton said.

“We never stop talking about some aspect of our work. You can look at that as an advantage,” Ellerton said with a smile, “or you can look at that as a disadvantage.”

Staying busy

They share a unique appreciation for the power of education. Clements was the only one of his 83 cousins to finish high school and go to college. Ellerton’s father taught in the equivalent of a one-room schoolhouse on the rough, isolated Australian outback. Neither came from money, and both spent years teaching in the classroom before moving into academia and consulting on education issues internationally. They’ve continued direct student contact through special projects, such as a summer program for high schoolers on Chicago’s south side, among others.

On top of their normal teaching schedules at Illinois State, they’re prolific publishers. Clements has co-edited three international handbooks on mathematics education and written or edited 21 other books and more than 200 articles. Ellerton is currently associate editor for the National Council of Teachers of Mathematics’ Journal for Research in Mathematics Education. (The Lincoln pages will be featured in Abraham Lincoln’s Cyphering Book, and Seven Other Extraordinary Cyphering Books, one of two books the couple is writing now that are expected to be published in 2014 by Springer.)

They love traveling to conferences together and get some of their best work done on road trips. Once on the way back to Bloomington from Chicago, Clements helped Ellerton prepare for an upcoming conference in Europe on the theories of mathematics education by verbally sketching out a diagram with her. When they got home, they put it on paper.

Sure beats listening to the radio.

“If we were working separately, it would have been much harder to develop it, in isolation,” Ellerton said.

When they’re not scouring the archives at Harvard for cyphering books that once belonged to former presidents, they keep busy with their hobbies. Clements seems to enjoy talking about his wife’s award-winning photography and poetry, or her skills as a restorer of old books, or that her “first Ph.D.” was in chemistry—a subject in which he is “hopeless.” And she’s quick to mention that he was a teenage chess champion, and was named in the Team of the Century for his local cricket association in Australia. They’re also big fans of Australian football, which they watch live online every week—usually at 4 a.m. or some odd hour because of the time change.

When you ask about why they care so much about the history of how math has been taught in this country—especially to a 16-year-old named Abe from Indiana—they give the same answer.

“Unless you are aware of your past, you’re going to repeat the failures of your past,” Clements told STATEside. “Unfortunately, in mathematics education, that’s happened far too often. You’re just seeing the same things being recycled. So what we’re trying to do is make people aware of patterns which have emerged—patterns which suggest strongly, ‘This is where you should be going.’”

Read more about Ellerton and Clements and their Lincoln announcement.

VIDEO: Here’s Ellerton and Clements at a press conference introducing their Lincoln findings:

Ryan Denham can be reached at rmdenha@IllinoisState.edu.