Momentary Concentration And Purification of Mind
By: 
Kheminda Thera (Ceylon)
There are three kind of concentration mentioned in the comentaries: "When bliss is conceived and matured it prefects the threefold concentration, that is, momentary concentration, access concentration, and absorption concentration". Of these, momentary concentrations the shortest in duration; next comes access contration; and thirdly absorption concentration which lasts the longest.

By way of occurrence, however, for the jhana-attainer developing insight, access concentration comes first; next comes fixed or absorption concentration followed by momenttary concentration thus:

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