Allotropy in Nitrogen and Bismuth of Group 15 Which elements of Group 15 of the periodic table have allotropes?  

P, As and Sb have well-known allotropes:  

P: White, Red and Black;
As: Yellow, Black and Gray (Grey);
Sb: White, Yellow and Black.          

What about Nitrogen and Bismuth?    


The same source suggests that Nitrogen has an allotrope named Dinitrogen while Bismuth has none.  
Chemwiki says:  


  $\ce{N2}$ does not have any allotropes.


and doesn't comment on Bismuth.
Royal Society of Chemistry says yes for Nitrogen and no for Bismuth.  
Inorganic Reactions and Methods: The Formation of Bonds to N, P, As, Sb, Bi (Part 1), Volume 7 has an article which suggests that Bismuth allotrope exists.  
This not so reliable source says no for Bismuth.
Wikipedia doesn't mention anything for Bismuth but for Nitrogen:  


  At atmospheric pressure, molecular nitrogen condenses (liquefies) at $\pu{77 K}$ ($\pu{−195.79^\circ C}$) and freezes at $\pu{63 K}$ ($\pu{−210.01^\circ C}$) into the beta hexagonal close-packed crystal allotropic form.  
  
  Unstable allotropes of nitrogen consisting of more than two nitrogen atoms have been produced in the laboratory, like $\ce{N3}$ and $\ce{N4}$. Other (as yet unsynthesized) allotropes include hexazine and octaazacubane.  



According to me, nitrogen has allotropes and bismuth doesn't, but the above sources contradict. Any clarifications and reasons for them showing or not showing allotropy would be appreciated.
Bismuth certainly has other known crystal structures at elevated pressures and temperatures, at least 4 others in addition to the rhombohedral structure stable at room temperature and pressure.  One place to start would be an article from NIF on shock physics of bismuth. For a scholarly article, you might start with 'Phase Diagrams of Arsenic, Antimony, and Bismuth at Pressures up to 70 kbars', W. Klement et al., Phys Rev 131(2) 632-637 (1963).

As for nitrogen, it too would appear to exhibit a variety of solid diatomic phases under pressure.  A starting point to explore might be 'High-pressure amorphous nitrogen', E. Gergoryanz et al., Phys Rev. B64 052103 (2001), which mentions a variety of phases in addition to the titular amorphous phase they explore.

Both Physical Review articles should be available to the general public...