1
2
Έκδοση: 1946
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 278
3
4
Έκδοση: 1939
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 181
5
Έκδοση: 1944
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 263
6
Έκδοση: 1935
Superior document: Annals of the Astronomical Observatory of Harvard College 89,6
7
Έκδοση: 1937
Superior document: Annals of the Astronomical Observatory of Harvard College 89,8
8
Έκδοση: 1946
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 281
9
Έκδοση: 1932
Superior document: Annals of the Astronomical Observatory of Harvard College 89,2
10
Έκδοση: 1952
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series II 41
11
12
Έκδοση: 1926
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 34
13
Έκδοση: 1936
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 123
14
15
Έκδοση: 1944
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 267
16
17
18
Έκδοση: 1933
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series I 91
19
Έκδοση: 1956
Superior document: Reprints / The Astronomical Observatory of Harvard College : Series II 98
20