SynopsisThe Fibonacci groups F(r, n) have been studied by various authors, chiefly in order to determine which ones are finite. This article contains a summary of the known results about this problem, followed by some further results obtained by the author. In particular, the orders of the groups F(r, 3) for r ≡ 2 (mod 3) and F(r, 4) for r ≡ 2 (mod 4) are determined, and various other Fibonacci groups are proved infinite by methods similar to those of Chalk and Johnson.

Sir, I note that in their paper describing the treatment of recurrent erosions of the cornea, l Bernauer et al. dismiss mechanical debridement of the cornea as a method of treatment of recalcitrant cases. However, they may have proved its efficacy. Before they can claim that excimer laser treatment has any added benefit, they really need to do a controlled trial to compare debridement followed by laser, with debridement alone.

obtained with positive samples may be reduced to near reagent blank values in this way and false-negative results obtained. Careful mixing of the contents of the tube by gentle inversion two or three times after the addition of the CPC reagent and again immediately prior to reading the absorbance is essential to obtain consistent results. This test can be used as the initial discriminatory procedure in the investigation of mucopolysaccharidoses and it is important that other users performing this test are made aware that the "insoluble" CPC-precipitable mucopolysaccharide can redissolve if not handled carefully. This could also be a source of error in the quantitative hexuronic acid method' for estimating mucopolysaccharides, which also has an initial CPC precipitation step.