“…We note that experimental determination of phases is an active area of research (see, for example, Shen & Colella, 1986;Hiimmer, Weckert & Bondza, 1990;Spence, 1993), although the only useful results (for the purposes of charge density analysis) appear to be measurements of the phase of the 002 reflection (with estimated error 0.07 °) in CdS (Zuo, Spence & Hoier, 1989) and the 002 reflection in BeO [with estimated error 0.52 ° (Zuo, Spence, Downs & Mayer, 1993)]; for organics, triplet phases can be determined with an accuracy of -,~45 ° (Htimmer et al, 1990).…”