Siddur Rashi, Section 587
I saw someone eat an udder before a milk meal and it should be prohibited to eat milk in that meal if he didn't clean his teeth or wait enough time for the meat between his teeth to be removed.
And between one meal and the next meal there is no measure, and he may even eat in the next meal milk.
Tosafot Hullin 104b
Rabbenu Tam explained, and so too it is found in Halakhot Gedolot (a Babylonian 10th century work) that if one ate meat, it is forbidden for him to eat cheese. This means without washing his hands or cleaning out his mouth.
If he ate cheese, he may eat meat afterwards without washing his hands or cleaning out his mouth.
And Mar Ukba who would not eat until another meal, this is if he did not wash his hands or clean his mouth.
Alternatively, he was more stringent than is necessary.
The common custom is not to eat cheese after meat at all, and even after chicken. And even though Agra taught that chicken and cheese can be eaten freely, which seems to mean chicken first, perhaps this is because he held that the prohibition of chicken and milk is not from the Torah. But we do not hold that way.
Issur Veheter of the Maharshal, 76
Many have the custom to be lenient and make for themselves a compromise to wait one hour after a meat meal, and remove the food, recite Birkat Hamazon, and then eat cheese.
And even though there is no reason for this nor is there any hint anywhere of this amount of time to wait, in any case, who is going to tell them that they're wrong, since the Tosafot and the Ra'avyah would permit this.
Those who are more religious wait from the morning meal [eaten at the middle of the day] until the evening meal.
The common custom is that even when one eats chicken one does not eat cheese afterwards, and there is no distinction between chicken and the meat of animals.
The Taz on the Shulkhan Arukh
Until he waits six hours: There are two reasons for this: 1) Meat is fatty and its taste remains in one's mouth for a long time. ...
And the second reason is the reason given by the Rambam, because of meat stuck between his teeth which is still considered meat for six hours and afterwards it is considered to be digested.
And there are those who eat cheese after one hour. [He now quotes the source from the Maharshal above].
And the Maharshal himself was surprised by this--how can people be lenient against the Rif and the Rambam who mandated waiting at least six hours. And he wrote that those who wait six hours like the Rambam and not the Tosafot who are permissive are acting well.
And he also wrote that if its impossible to protest against those who are not "Bnei Torah" we can protest against those who are Bnei Torah, and rebuke them not to be more lenient than six hours.