Complete Works of Euclid, Vol. 6 (Optics, Catoptrics, etc.)

P^2 — scholia of codex P by two or three more recent hands, but yet in part quite old, written in the free margins or, where space was lacking, on slips of cheaper parchment stitched in here and there.
P^3 — a few scholia in P written negligently in the margin by a very recent hand.
F — scholia of codex F by the first hand, written in uncial letters with very many abbreviations, some of which have faded.
F^2 — scholia of codex F added by a more recent hand.
B — scholia of codex B by a hand contemporary with the codex itself, undoubtedly for the most part Arethas' (see Maas, Mélanges Graux p. 754), but written at different times and in different ink elsewhere, and not all at the same time.
B^1 — scholia of codex B by a sufficiently old hand, written in dark ink, which is, however, somewhat more recent than the first hand; for on fol. 180v (schol. to X, 6 no. 51) it repeats the beginning of the first hand's scholium, undoubtedly because even then it was difficult to read. The same hand sometimes uses paler ink (for on fol. 179v and fol. 195r the same scholium is written at the end in dark ink, at the beginning in pale ink).
B^2 — scholia of codex B by a recent hand in brown ink.
B^3 — scholia of codex B by another recent hand in greyish ink.
B^4 — scholia of codex B written by a very recent and negligent hand. This hand, except for certain trifles ($δι\dot{α}$ $τ\acute{o}$, etc.), wrote nothing outside book X. B^2 is rarer and hardly goes beyond book II.