A set of lecture notes affectionately known as “Joe’s Little Book of [these systems]” is a companion to Polchinski’s textbook on these systems. Considering all surfaces of genus one under the Polyakov path integral constitutes the one-level analysis of these systems, whose simplest invariant model is the Nambu–Goto (15[1])action. (15[1])These systems (15[2])trace out worldsheets (15[1])in spacetime, (15[4]-5[1])and their boundary conditions create D-branes. Ed (15[5])(*) Witten (10[4])combined (10[2])several (10[1])related theories (10[1])of these (10[3])systems (10[2]-5[1])with supergravity (10[1])into the (10[2])11-dimensional (10[5])M-theory, (10[5])providing a unification (10[2]-5[1])of quantum (-5[1])mechanics with (-5[1])general (10[1])relativity. (10[1])Particles are envisioned as vibrational modes (10[2])of (10[1])these systems (10[1])in those (10[1])namesake theories. (10[2]-5[1])For 10 points, name these one-dimensional systems that form the basis of an unverifiable theory of everything. (10[1])■END■ (10[5]0[1])