5.     Recommendations I.440, I.441, I.450, I.451 and I.452

5.1    Recommendation I.440 - ISDN user-network interface data link  layer  -
general aspects (see Recommendation  Q.920,  Volume  VI,  Fascicle    of  the
Blue Book)

5.2    Recommendation I.441 - ISDN user-network interface,  data  link  layer
specification (see Recommendation G.921, Volume VI, Fascicle   of the Blue Book)

5.3    Recommendation I.450 - ISDN user-network interface layer 3  -  general
aspects (see Recommendation Q.930, Volume VI, Fascicle   of the Blue Book)

5.4     Recommendation  I.451  -  ISDN   user-network   interface   layer   3
specification for basic call control (see Recommendation Q.931, Volume VI, Fascicle   of 
the Blue Book)

5.5     Recommendation  I.452  -  ISDN   user-network   interface   layer   3
specification - generic procedures for the control of the ISDN supplementary services 
(see Recommendation Q.932, Volume VI Fascicle   of the Blue Book).