The books are geared toward kids ages 4 through 12 who have health issues and could use a few laughs. (Marci Schmitt — Getty Images/iStockphoto/The Minnesota Star Tribune)

Not only may laughter be the best medicine, but it also can help pay the medical bills.

Have you heard this one? What does a Norwegian dog say? Woof-da.

Granted, humor is subjective thing. But UnitedHealthcare has released three joke books with a serious purpose.

The books are geared toward kids ages 4 through 12 who have health issues and could use a few laughs. Funds raised from book sales also go toward helping pay for health care expenses not covered, or not fully covered, by a commercial health insurance plan.

"We wanted to create a fun, kid-inspired fundraiser that gave kids recognition for helping others," said Will Holman, a spokesman for UnitedHealthcare Children's Foundation in Minneapolis. "Being a published author is pretty cool for a kid, too, especially knowing you're raising funds to help provide child medical grants to families in need."

Hundreds of kids from around the country sent in their best jokes, which then were sorted into three books, "Cool Jokes for Summer," "Eats, Treats & Sweets" and "Birthday, Holiday & Celebration Jokes." Among them are jokes from 94 Minnesota children; thank Isabelle Einess of Minneapolis for the Norwegian dog joke.

Or how about this one from Deepak Balasubramani of Eden Prairie: Why is the zebra striped? Because it didn't want to be spotted.

Choosing the more than 300 jokes in each book was, well, a laughing matter.

Holman said a team evaluated the submissions. In the case of duplicates, the joke submitted first got the nod. "For those children who submitted a duplicate joke, we did reach back out to those families and encouraged them to consider submitting another joke," he said.

A news release said some of the humor "will bring back fond childhood memories for all," which is a nice way of saying some jokes — notably knock-knocks — never die. From Cole Hustad of Minneapolis:

Knock knock.

Who's there?

Atch.

Atch who?

Bless you!

The books are available on Amazon for $5.99 each. Holman said that it's too soon to measure their financial impact but that UnitedHealthcare also hopes that the books raise public awareness that child medical grants are available, so more families apply for them.

UnitedHealthcare Children's Foundation has awarded more than 14,000 grants valued at more than $38 million to children and their families across the United States. Families do not need to have insurance through UnitedHealthcare to be eligible for a grant. Visit uhccf.org to learn more.

In any case, keep in mind the message behind this submission from Vineet Khichadia of Eden Prairie: If you know any vegetable jokes, please lettuce know.

Hundreds of kids from around the country sent in their best jokes, which then were sorted into three books. (The Minnesota Star Tribune)