A Maya Angelou stamp that will be issued Tuesday features a quote attributed to her. Did another writer say it first? (U.S. Postal Service)

The news that the U.S. Postal Service was honoring Maya Angelou, poet, author and civil rights advocate, with her own forever stamp was welcomed by her fans. Angelou, who died last year, was a cultural icon and mother figure to a generation of writers.

Jabari Asim, associate professor of writing, literature and publishing at Emerson College in Boston, was excited. Until he read the quote on the Angelou stamp:

“A bird doesn’t sing because it has an answer, it sings because it has a song.”

Funny thing, he had always thought the quote came from Joan Walsh Anglund, the prolific children’s book author.

Asim, a former editor for The Washington Post’s Book World, had seen the quote attributed to Angelou on social media but was highly skeptical. The Internet is full of misattributions. But the Postal Service?

When the stamp, which will be issued Tuesday, was announced, he started tracking the quote down. He went to a notebook of quotes he has collected from writers, thinkers, “anything that appeals to me or resonates with me,” for 18 years. “I knew I had that quote . . . and there it was. It said Joan Walsh Anglund.” Asim is meticulous about attribution, so “I knew that however many years ago I put that in there, I had taken care to find a source.”

The exact quote — the one that appears on the Angelou forever stamp — also appears on Page 15 in the book “A Cup of Sun,” by Joan Walsh Anglund, copyright 1967.

According to Postal Service spokesman Mark Saunders, the post office’s research team said the quote had “come up in different media interviews Maya Angelou had done” and that using it had been approved by her family members. He didn’t know which ones.

Last year, in remarks at the presentation of the 2013 National Medal of Arts and National Humanities Medal, President Obama attributed the quote to Angelou:

“The late, great Maya Angelou once said, ‘A bird doesn’t sing because it has an answer, it sings because it has a song.’ Each of the men and women that we honor today has a song — literally, in some cases. For others, it’s a talent, or a drive, or a passion that they just had to share with the world.”

Saunders, who hadn’t heard of the Anglund quote, sent a link to an interview that Angelou gave to a blog dedicated to the blues. The 2013 blog post quotes Angelou saying: “I wrote the book because ‘Bird Sings Why The Caged I Know’ [sic] is a song. A bird doesn’t sing because it has an answer it sings because it has a song.”

I asked Saunders if the post office had any other sources for the quote. He sent this statement in response:

“Maya Angelou was widely quoted as saying, ‘A bird doesn’t sing because it has an answer, it sings because it has a song.’

“There are numerous references in books, magazines, blogs and on the internet crediting Angelou with having said it as well.

“The Postal Service used her widely recognized quote to help build an immediate connection between her image and her 1969 nationally recognized autobiography, ‘I Know Why the Caged Bird Sings.’ ”

Attempts to reach Anglund were unsuccessful.

Beyond deeper questions of when Angelou first said or wrote the quote are the questions of how it comes to appear on a government-issued stamp — one called “forever,” no less.

It leaves unanswered questions about the cut-and-paste nature of the Internet, where it is always possible to unintentionally take one person’s comment and attribute it to someone else.

Sometimes, the quote “We are what we repeatedly do. Excellence, then, is not an act, but a habit” is attributed to Shaquille O’Neal. But it also gets attributed to Aristotle. In 2012, a quote on the Martin Luther King Jr. National Memorial was deemed inaccurate and had to be re-chiseled.

Liana Asim, playwright and wife of Jabari, says that when she saw the quote on the Internet, it didn’t sound like Angelou. “Her rhythm and her cadence are things you don’t hear in other places.”

For Jabari Asim, the disappointment is that Angelou is “eminently quotable. You can flip open one of her books at random and pull out something.

“So I’d rather she be remembered for her own words. It’s more about preserving the legacy of Maya Angelou than pointing out misattributions.”

He references an often-circulated meme: “Don’t believe everything you read on the Internet just because there’s a picture with a quote next to it.” The meme features a picture of President Abraham Lincoln. Perhaps that should be a stamp.

Magda Jean-Louis contributed to this column. For more by O’Neal, visit wapo.st/lonnae.