There are four sub-classes or flights of Shchuka, consisting of the original seven "Akula I" submarines which were commissioned between 1984 and 1990, six "Improved Akula" submarines commissioned between 1991 and 2009, one "Akula II" submarine commissioned in 1995 and one "Akula III" commissioned in 2001.
== Zunanje povezave ==* Royal Australian Navy 805 Squadron Skyhawk information* A-4 Skyhawk page on Boeing.com* RNZAF Museum Skyhawk page* Serial number history of Australian A-4 Skyhawks, prefix N13* A-4 at Combat Air Museum* A-4 Skyhawk from reference book "American Combat Planes of the 20th Century" by R. Wagner* AeroWeb.org A-4 Skyhawks on display* restoration to flight of a TA-4J* (1962) NAVWEPS 01-40AVA-1 Flight Handbook Navy Model A4D-1 and A4D-2 Aircraft* "A-4D Skyhawk" a 1958 "Flight" article