Let me add to the others: after either 1c - 1d or 1d - 2c
responder's only weak rebids are in the minors. Anything
else requires at least 9 HCP. This is particularly
striking in B-3 where
1c - 1d
1M - 1NT
promises 9-11 HCP. With 5-8 balanced, responder should
have bid 1NT rather than 1D.
With a 5-8 5c-3-3-2 you must respond 1NT to 1d. In his
original KS book, EK recommended that opener rebid 2c
holding the like of 1=4=5=3. Note that there must be an
8-card fit in one of the minors. Also, while one could
wind up in a 7-card fit, it's never happened to me in
practice, and it has scored well, even at match points.
Fred.