Pattern recognition letters

Articles in SafetyLit
Y-Axis = Volume :: X-Axis = Issue
?=unknown status :: X=no issue published :: nn=articles from issue :: A=relevant article(s) IDed to add
S=searched, nothing relevant :: O=issue published but not yet searched :: C=combination issue

		1	2	3	7

23 (2002)	?	1	?	C	?
27 (2006)	?	1	?	?	1
29 (2008)	?	?	?	?	1
30 (2009)	?	?	2	?	?
31 (2010)	?	?	?	1	?
32 (2011)	?	?	2	?	?
33 (2012)	?	?	?	1	?
107 (2017)	1	?	?	?	?
110 (2018)	1	?	?	?	?