Aggregation of SEP Plan with 403(b), 401(a) for 415 limits

[Guest kprhok]

It is my understanding that contributions to 403(b) and Keogh for self-employed persons must be aggregated for calculation of the 415 limit, but that a separate 415 limit would apply if the individual also participated in a qualified plan (i.e. a university), for a possible total 90k limit.

Am I correct?

Does the situation change if the individual has a SEP-IRA instead of a Keogh as a consultant apart from his work at the institution, or does the same result occur.... 45k total for the SEP and 403(b), and a separate 45k for the institution's qualified plan?

Thank you. Any citations to reference materials that explain how aggregation works across many plan types would be great.