Letter	Sub heading
A	English studies generally
B	English language
BE	Anglo-Saxon language: to 1050
BM	Middle English language: 1050 - 1500
C	English literature generally
CC	Scottish literature generally
D	Anglo-Saxon: to 1066
E	Middle English: 1066 - 1485
G	Early Tudor: 1485 - 1580
H	Later Tudor: 1580 - 1603
HS	Shakespeare
J	Jacobean; Caroline & Commonwealth: 1603 - 1660
K	Restoration: 1660 - 1700
L	Early 18th century: 1700 - 1750
M	Later 18th century: 1750 - 1800
N	Early 19th century: 1800 - 1837
P	Early Victorian: 1837 - 1875
Q	Later Victorian; Edwardian: 1875 - 1914
R	20th century: 1914 - 1950
S	20th century: 1950 -
X	American literature
XA	American studies generally
XC	American literature generally
XJ	Colonial & Revolutionary periods: to 1800
XN	19th century
XR	20th century: 1900 - 1950
XS	20th century: 1950 -