ChemInform Abstract: Synthesis, Crystal Structure and Catalytic Activity of the Guanidinium Cation Directed Nickel(II)‐Containing Open Wells—Dawson 19‐Tungstodiarsenate(III) [{Ni(H2O)4}2{Na (H2O)}As2W19O67(H2O)] 9‐. Issue 25 (5th June 2015)