Medicare denial remarks

Does anyone have an resources that may further explain Medicare denial remarks? I have gotten a couple today that I haven't received before and would love some help. Or if any of you may know..

N270 - Missing/incomplete/invalid other provider primary identifier
N283 - Missing/incomplete/invalid purchased service provider identifier.

I billed:
99214 - 25
81003
36415-90
84153
51798

All fields are completed on the HCFA. Provider and referring provider information is correct. Any ideas?

re: Medicare denial remarks

http://www.wpc-edi.com/reference/codelists/healthcare/remittance-advice-remark-codes/

re: Medicare denial remarks

I've seen this page but it doesn't tell me what the remark codes mean exactly.