Selecting different tables in nHibernate

Selecting different tables in nHibernate

I need to execute a query that will return N tables. in my program, i have
the following tables (some of them):
TABLES:
HM_RECEIVE;
HM_SEND;
SM_RECEIVE;
SM_SEND;
P_SLAB;
P_SLAB_PDO;
...
Entities:
HMreceive;
HMsend;
SMreceive;
SMsend;
PSlab;
PSlabPDO;
...
I have two questions, and this would be nicer if i could accomplish it
using only one criteria:
How do I select all tables? In first moment I believe there's no need to
match IDs, but if changes anything I really would like to know;
Is there a way to select only HM and SM tables, ignoring all others?
Thanks in advance.