Methods in Enzymology, Volume 551. Circadian Rhythms and Biological Clocks, Part A. Edited by Amita Sehgal. Academic Press. Amsterdam (The Netherlands) and Boston (Massachusetts): Elsevier. $199.00. xviii + 470 p. + 16 pl.; ill.; author and subject indexes. ISBN: 978-0-12-801218-5. 2015.Methods in Enzymology, Volume 552. Circadian Rhythms and Biological Clocks, Part B. Edited by Amita Sehgal. Academic Press. Amsterdam (The Netherlands) and Boston (Massachusetts): Elsevier. $199.00. xviii + 395 p. + 16 pl.; ill.; author and subject indexes. ISBN: 978-0-12-803380-7. 2015.