The Concise Oxford Dictionary of World Religions (1304 page)

(i) 
hosshin-k
an
, to create awareness of identity with buddha-nature (
bussho
);
(ii) 
kikan-k
an
, to create ability nevertheless to discern distinctions within non-distinction;
(iii) 
gonsen-k
an
, creating awareness of the deep meaning of the sayings of the masters;
(iv) 
nant
-k
an
, grappling with the hardest to solve;
(v) 
go-i-k
an
: when the other four have been worked through, the insight gained is tested once more