Education officials said they were investigating a "credible report" that students at one school had seen those math questions in advance.
There are also credible reports of hunger and malnutrition in some rural areas.
We have even heard credible reports recently of women being buried alive in the eastern Congo.
There have been highly credible reports of arrests here, particularly at the city's several research institutes and universities.
And, he said, "there are growing numbers of credible reports of innocent people being killed in the last two or three weeks."
First they were rumours, then more credible reports and finally we received confirmation that he had died.
There have been credible reports of mountain lion sightings in these areas recently.
Cameron says there are credible reports of 1,000 dead in Syria.
Furthermore, there were many credible reports of direct atrocities against the population.
There were credible reports of government interference with religious travel.