Books:
1. Alan Hastings "Art of analog layout"
2. Baker, Li, Boyce "CMOS circuit, design, layout and simulations"
Articles:
Any papers about current steering DACs, e.g.:
1. C. Bastiaansen, D. Groeneveld, H. Schouwenaars, H. Termeer "A 10-b 40-MHz 0.8-um CMOS current-output D/A converter." IEEE Solid State Circuits, vol. 26, no 7, 1991, pp 917 - 921
But in briefly example of two transistors:
1. Interdigitized:
ABAB
2. Common centroid:
ABBA
In common centroid the transistors placement is around one point of symmetry, while in interdigitized are alternately (layout of multifinger fet is a good example)