This page lists the standard references that guide the development of Icarus Verilog. This is broken into 2 lists: The official language reference manuals, and other useful references.
These define the official references. These documents define the language and its variants.
IEEE Std 1364-2005
Otherwise known as the IEEE Standard for Verilog Hardware Description Language, this is the bible for the Verilog language. It is available for purchase from the IEEE. This updates the IEEE1364-2001, so in most cases the older 2001 version of the standard is an adequate substitute.
IEEE Std 1800-xxxx
This is the SystemVerilog standard. Icarus Verilog currently supports little of the SystemVerilog language, but those features above the basic Verilog that are covered by SystemVerilog are kept compatible with this standard.
Verilog AMS Language Reference Manual
This has no IEEE number, and the LRM itself is available for free download from the Verilog-AMS documents page.
Icarus Verilog is currently working with version 2.3.