Sample Letter to Credit Bureau???

I first sent requests for debt validation to collection agencies that were on my credit report. 30+ days later, I sent those that have not verified the debt a follow-up letter.

Should I also send a letter to the credit bureaus to request that they validate the debt? What is a good sample letter?

Also, should I send the credit bureau one letter for all the collection accounts or should I do it individually?

Thanks in advance!!!