LMucko/crystallography-open-database huggingface dataset:
The crystal structure of CaHAsO4 (weilite)
Ferraris, G.; Chiari, G.; Acta Crystallographica, Section B 26 (1970) 403–409; doi:10.1107/S0567740870002467

data_9007511
_publ_section_title
;
 The crystal structure of CaHAsO4 (weilite)
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              403
_journal_page_last               409
_journal_paper_doi               10.1107/S0567740870002467
_journal_volume                  26
_journal_year                    1970
_chemical_compound_source        Synthetic
_chemical_formula_sum            'As2 Ca2 H2 O8'
_chemical_name_mineral           Weilite
_space_group_IT_number           2
_symmetry_space_group_name_Hall  '-P 1'
_symmetry_space_group_name_H-M   'P -1'
_cell_angle_alpha                97.43
_cell_angle_beta                 103.55
_cell_angle_gamma                87.75
_cell_formula_units_Z            2
_cell_length_a                   7.0591
_cell_length_b                   6.8906
_cell_length_c                   7.2006
_cell_volume                     337.625
_database_code_amcsd             0009369
_exptl_crystal_density_diffrn    3.541
_cod_original_formula_sum        'Ca2 As2 O8 H2'
_cod_database_code               9007511
The crystal structure of fairfieldite
Fanfani, L.; Nunzi, A.; Zanazzi, P. F.; Acta Crystallographica, Section B 26 (1970) 640–645; doi:10.1107/S0567740870002893

data_9007512
_publ_section_title
;
 The crystal structure of fairfieldite
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              640
_journal_page_last               645
_journal_paper_doi               10.1107/S0567740870002893
_journal_volume                  26
_journal_year                    1970
_chemical_compound_source        'Foote Mine, North Carolina, USA'
_chemical_formula_sum            'Ca2 H4 Mn O10 P2'
_chemical_name_mineral           Fairfieldite
_space_group_IT_number           2
_symmetry_space_group_name_Hall  '-P 1'
_symmetry_space_group_name_H-M   'P -1'
_cell_angle_alpha                102.27
_cell_angle_beta                 108.67
_cell_angle_gamma                90.30
_cell_formula_units_Z            1
_cell_length_a                   5.79
_cell_length_b                   6.57
_cell_length_c                   5.51
_cell_volume                     193.428
_database_code_amcsd             0009374
_exptl_crystal_density_diffrn    3.100
_cod_original_formula_sum        'Ca2 Mn P2 O10 H4'
_cod_database_code               9007512
Unit cell and crystal structure of nordstrandite, Al(OH)3
Bosmans, H. J.; Acta Crystallographica, Section B 26 (1970) 649–652; doi:10.1107/S0567740870002911

data_9007513
_publ_section_title
;
 Unit cell and crystal structure of nordstrandite, Al(OH)3
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              649
_journal_page_last               652
_journal_paper_doi               10.1107/S0567740870002911
_journal_volume                  26
_journal_year                    1970
_chemical_compound_source        Synthetic
_chemical_formula_sum            'Al H3 O3'
_chemical_name_mineral           Nordstrandite
_space_group_IT_number           2
_symmetry_space_group_name_Hall  '-P 1'
_symmetry_space_group_name_H-M   'P -1'
_cell_angle_alpha                70.27
_cell_angle_beta                 74.0
_cell_angle_gamma                58.47
_cell_formula_units_Z            2
_cell_length_a                   5.114
_cell_length_b                   5.082
_cell_length_c                   5.127
_cell_volume                     106.089
_database_code_amcsd             0009375
_exptl_crystal_density_diffrn    2.442
_cod_original_formula_sum        'Al (O3 H3)'
_cod_database_code               9007513
The crystal structure of anilite
Koto, K.; Morimoto, N.; Acta Crystallographica, Section B 26 (1970) 915–924; doi:10.1107/S0567740870003370

data_9007514
_publ_section_title
;
 The crystal structure of anilite
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              915
_journal_page_last               924
_journal_paper_doi               10.1107/S0567740870003370
_journal_volume                  26
_journal_year                    1970
_chemical_formula_sum            'Cu7 S4'
_chemical_name_mineral           Anilite
_space_group_IT_number           62
_symmetry_space_group_name_Hall  '-P 2ac 2n'
_symmetry_space_group_name_H-M   'P n m a'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   7.89
_cell_length_b                   7.84
_cell_length_c                   11.01
_cell_formula_units_Z            4
_cell_volume                     681.052
_database_code_amcsd             0009376
_exptl_crystal_density_diffrn    5.589
_cod_database_code               9007514
On the crystal chemistry of salt hydrates. VI. The crystal structures of disodium hydrogen orthoarsenate heptahydrate and of disodium hydrogen orthophosphate heptahydrate
Baur, W. H.; Khan, A. A.; Acta Crystallographica, Section B 26 (1970) 1584–1596; doi:10.1107/S0567740870004521

data_9007515
_publ_section_title
;On the crystal chemistry of salt hydrates. VI. The crystal structures of
 disodium hydrogen orthoarsenate heptahydrate and of disodium hydrogen
 orthophosphate heptahydrate
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1584
_journal_page_last               1596
_journal_paper_doi               10.1107/S0567740870004521
_journal_volume                  26
_journal_year                    1970
_chemical_formula_structural     Na2HAsO4*7H2O
_chemical_formula_sum            'As H15 Na2 O11'
_space_group_IT_number           14
_symmetry_space_group_name_Hall  '-P 2yn'
_symmetry_space_group_name_H-M   'P 1 21/n 1'
_cell_angle_alpha                90
_cell_angle_beta                 95.50
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   9.401
_cell_length_b                   11.025
_cell_length_c                   10.674
_cell_volume                     1101.224
_database_code_amcsd             0009378
_exptl_crystal_density_diffrn    1.882
_cod_original_formula_sum        'Na2 As O11 H15'
_cod_database_code               9007515
_amcsd_formula_title             Na2HAsO4*7H2O
On the crystal chemistry of salt hydrates. VI. The crystal structures of disodium hydrogen orthoarsenate heptahydrate and of disodium hydrogen orthophosphate heptahydrate
Baur, W. H.; Khan, A. A.; Acta Crystallographica, Section B 26 (1970) 1584–1596; doi:10.1107/S0567740870004521

data_9007516
_publ_section_title
;On the crystal chemistry of salt hydrates. VI. The crystal structures of
 disodium hydrogen orthoarsenate heptahydrate and of disodium hydrogen
 orthophosphate heptahydrate
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1584
_journal_page_last               1596
_journal_paper_doi               10.1107/S0567740870004521
_journal_volume                  26
_journal_year                    1970
_chemical_formula_structural     Na2HPO4*7H2O
_chemical_formula_sum            'H15 Na2 O11 P'
_space_group_IT_number           14
_symmetry_space_group_name_Hall  '-P 2yn'
_symmetry_space_group_name_H-M   'P 1 21/n 1'
_cell_angle_alpha                90
_cell_angle_beta                 95.61
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   9.258
_cell_length_b                   11.007
_cell_length_c                   10.437
_cell_volume                     1058.466
_database_code_amcsd             0009379
_exptl_crystal_density_diffrn    1.682
_cod_original_formula_sum        'Na2 P O11 H15'
_cod_database_code               9007516
_amcsd_formula_title             Na2HPO4*7H2O
Strukturverfeinerung von enargit, Cu3AsS4
Adiwidjaja, G.; Lohn, J.; Acta Crystallographica, Section B 26 (1970) 1878–1879; doi:10.1107/S0567740870005034

data_9007517
_publ_section_title
;
 Strukturverfeinerung von enargit, Cu3AsS4
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1878
_journal_page_last               1879
_journal_paper_doi               10.1107/S0567740870005034
_journal_volume                  26
_journal_year                    1970
_chemical_compound_source        'Butte, Montana, USA'
_chemical_formula_sum            'As Cu3 S4'
_chemical_name_mineral           Enargite
_space_group_IT_number           31
_symmetry_space_group_name_Hall  'P 2ac -2'
_symmetry_space_group_name_H-M   'P m n 21'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   7.407
_cell_length_b                   6.436
_cell_length_c                   6.154
_cell_formula_units_Z            2
_cell_volume                     293.370
_database_code_amcsd             0009381
_exptl_crystal_density_diffrn    4.458
_cod_original_formula_sum        'Cu3 As S4'
_cod_database_code               9007517
Determination of hydrogen atom positions in the crystal structure of pharmacolite, CaHAsO4(H2O)2, by neutron diffraction
Ferraris, G.; Jones, D. W.; Yerkess, J.; Acta Crystallographica, Section B 27 (1971) 349–354; doi:10.1107/S0567740871002206

data_9007518
_publ_section_title
;
 Determination of hydrogen atom positions in the crystal structure of
 pharmacolite, CaHAsO4(H2O)2, by neutron diffraction
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              349
_journal_page_last               354
_journal_paper_doi               10.1107/S0567740871002206
_journal_volume                  27
_journal_year                    1971
_chemical_compound_source        'Andreasberg, Harz Mts, Lower Saxony, Germany'
_chemical_formula_sum            'As Ca H5 O6'
_chemical_name_mineral           Pharmacolite
_space_group_IT_number           9
_symmetry_space_group_name_Hall  'I -2ya'
_symmetry_space_group_name_H-M   'I 1 a 1'
_cell_angle_alpha                90
_cell_angle_beta                 114.83
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   5.9745
_cell_length_b                   15.4340
_cell_length_c                   6.2797
_cell_volume                     525.525
_database_code_amcsd             0009386
_exptl_crystal_density_diffrn    2.730
_cod_original_formula_sum        'Ca As O6 H5'
_cod_database_code               9007518
The crystal structure of 2-dimenthylsulfuranylidene-1,3-indanedione
Christensen, A. T.; Thom, E.; Acta Crystallographica, Section B 27 (1971) 581–586; doi:10.1107/S0567740871002590

data_9007519
_publ_section_title
;
 The crystal structure of 2-dimenthylsulfuranylidene-1,3-indanedione
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              581
_journal_page_last               586
_journal_paper_doi               10.1107/S0567740871002590
_journal_volume                  27
_journal_year                    1971
_chemical_formula_sum            'C11 H10 O2 S'
_chemical_name_mineral           Ylid
_space_group_IT_number           19
_symmetry_space_group_name_Hall  'P 2ac 2ab'
_symmetry_space_group_name_H-M   'P 21 21 21'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   18.331
_cell_length_b                   9.012
_cell_length_c                   5.949
_cell_formula_units_Z            4
_cell_volume                     982.769
_database_code_amcsd             0009387
_exptl_crystal_density_diffrn    1.394
_cod_original_formula_sum        'C11 O2 S H10'
_cod_database_code               9007519
Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3 and relation to magnetic ordering
Geller, S.; Acta Crystallographica, Section B 27 (1971) 821–828; doi:10.1107/S0567740871002966

data_9007520
_publ_section_title
;
 Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3
 and relation to magnetic ordering
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              821
_journal_page_last               828
_journal_paper_doi               10.1107/S0567740871002966
_journal_volume                  27
_journal_year                    1971
_chemical_formula_structural     Mn2O3
_chemical_formula_sum            'Mn2 O3'
_space_group_IT_number           61
_symmetry_space_group_name_Hall  '-P 2bc 2ac'
_symmetry_space_group_name_H-M   'P c a b'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   9.4157
_cell_length_b                   9.4233
_cell_length_c                   9.4047
_cell_formula_units_Z            16
_cell_volume                     834.450
_database_code_amcsd             0009390
_exptl_crystal_density_diffrn    5.027
_cod_database_code               9007520
_amcsd_formula_title             Mn2O3
Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3 and relation to magnetic ordering Sample: (MnO.983Fe0.017)203
Geller, S.; Acta Crystallographica, Section B 27 (1971) 821–828; doi:10.1107/S0567740871002966

data_9007521
_publ_section_title
;
 Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3
 and relation to magnetic ordering
 Sample: (MnO.983Fe0.017)203
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              821
_journal_page_last               828
_journal_paper_doi               10.1107/S0567740871002966
_journal_volume                  27
_journal_year                    1971
_chemical_formula_sum            'Fe0.034 Mn1.966 O3'
_chemical_name_mineral           Bixbyite
_space_group_IT_number           206
_symmetry_space_group_name_Hall  '-I 2b 2c 3'
_symmetry_space_group_name_H-M   'I a -3'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   9.4146
_cell_length_b                   9.4146
_cell_length_c                   9.4146
_cell_formula_units_Z            16
_cell_volume                     834.460
_database_code_amcsd             0009391
_exptl_crystal_density_diffrn    5.028
_cod_original_sg_symbol_H-M      'I a 3'
_cod_original_formula_sum        '(Fe.034 Mn1.966) O3'
_cod_database_code               9007521
Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3 and relation to magnetic ordering Sample: (Mn0.37Fe0.63)2O3
Geller, S.; Acta Crystallographica, Section B 27 (1971) 821–828; doi:10.1107/S0567740871002966

data_9007522
_publ_section_title
;
 Structures of alpha-Mn203, (MnO.983Fe0.017)203 and (Mn0.37Fe0.63)2O3
 and relation to magnetic ordering
 Sample: (Mn0.37Fe0.63)2O3
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              821
_journal_page_last               828
_journal_paper_doi               10.1107/S0567740871002966
_journal_volume                  27
_journal_year                    1971
_chemical_formula_sum            'Fe1.26 Mn0.74 O3'
_chemical_name_mineral           Bixbyite
_space_group_IT_number           206
_symmetry_space_group_name_Hall  '-I 2b 2c 3'
_symmetry_space_group_name_H-M   'I a -3'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   9.4126
_cell_length_b                   9.4126
_cell_length_c                   9.4126
_cell_formula_units_Z            16
_cell_volume                     833.928
_database_code_amcsd             0009392
_exptl_crystal_density_diffrn    5.066
_cod_original_sg_symbol_H-M      'I a 3'
_cod_original_formula_sum        '(Fe1.26 Mn.74) O3'
_cod_database_code               9007522
A refinement of the structure of rhombohedral acetamide
Denne, W. A.; Small, R. W. H.; Acta Crystallographica, Section B 27 (1971) 1094–1098; doi:10.1107/S0567740871003583

data_9007523
_publ_section_title
;
 A refinement of the structure of rhombohedral acetamide
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1094
_journal_page_last               1098
_journal_paper_doi               10.1107/S0567740871003583
_journal_volume                  27
_journal_year                    1971
_chemical_compound_source        Synthetic
_chemical_formula_sum            'C2 H5 N O'
_chemical_name_mineral           Acetamide
_space_group_IT_number           161
_symmetry_space_group_name_Hall  'R 3 -2"c'
_symmetry_space_group_name_H-M   'R 3 c :H'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_length_a                   11.526
_cell_length_b                   11.526
_cell_length_c                   13.589
_cell_formula_units_Z            18
_cell_volume                     1563.419
_database_code_amcsd             0009394
_exptl_crystal_density_diffrn    1.129
_cod_original_sg_symbol_H-M      'R 3 c'
_cod_original_formula_sum        'C2 O N H5'
_cod_database_code               9007523
The crystal structure of aikinite, PbCuBiS3 Note: B(3,3) altered for Pb and Cu, in order to reproduce Biso
Kohatsu, I.; Wuensch, B. J.; Acta Crystallographica, Section B 27 (1971) 1245–1252; doi:10.1107/S0567740871003819

data_9007524
_publ_section_title
;
 The crystal structure of aikinite, PbCuBiS3
 Note: B(3,3) altered for Pb and Cu, in order to reproduce Biso
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1245
_journal_page_last               1252
_journal_paper_doi               10.1107/S0567740871003819
_journal_volume                  27
_journal_year                    1971
_chemical_formula_sum            'Bi Cu Pb S3'
_chemical_name_mineral           Aikinite
_space_group_IT_number           62
_symmetry_space_group_name_Hall  '-P 2ac 2n'
_symmetry_space_group_name_H-M   'P n m a'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_length_a                   11.608
_cell_length_b                   4.0279
_cell_length_c                   11.275
_cell_formula_units_Z            4
_cell_volume                     527.172
_database_code_amcsd             0009395
_exptl_crystal_density_diffrn    7.256
_cod_original_formula_sum        'Pb Cu Bi S3'
_cod_database_code               9007524
The crystal structure of rinkite
Galli, E.; Alberti, A.; Acta Crystallographica, Section B 27 (1971) 1277–1284; doi:10.1107/S056774087100387X

data_9007525
_publ_section_title
;
 The crystal structure of rinkite
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1277
_journal_page_last               1284
_journal_paper_doi               10.1107/S056774087100387X
_journal_volume                  27
_journal_year                    1971
_chemical_compound_source        'Kangerdluarsuk, Greenland'
_chemical_formula_sum
;Al0.089 Ca3.368 Ce1.048 F3 Fe0.212 K0.064 Na2.178 Nb0.327 O15 Si4 Ti0.515
 Zr0.069
;
_chemical_name_mineral           Rinkite
_space_group_IT_number           14
_symmetry_space_group_name_Hall  '-P 2ybc'
_symmetry_space_group_name_H-M   'P 1 21/c 1'
_cell_angle_alpha                90
_cell_angle_beta                 101.38
_cell_angle_gamma                90
_cell_length_a                   7.437
_cell_length_b                   5.664
_cell_length_c                   18.8430
_cell_formula_units_Z            2
_cell_volume                     778.122
_database_code_amcsd             0009396
_exptl_crystal_density_diffrn    3.497
_cod_original_formula_sum
'(Ti.515 Nb.327 Al.089 Zr.069) Na2.178 Ca3.368 K.064 Ce1.048 Fe.212 Si4 O15 F3'
_cod_database_code               9007525
The crystal structure of Zn2SiO4-II, a high-pressure phase of willemite
Marumo, F.; Syono, Y.; Acta Crystallographica, Section B 27 (1971) 1868–1870; doi:10.1107/S0567740871005004

data_9007526
_publ_section_title
;
 The crystal structure of Zn2SiO4-II, a high-pressure phase of willemite
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              1868
_journal_page_last               1870
_journal_paper_doi               10.1107/S0567740871005004
_journal_volume                  27
_journal_year                    1971
_chemical_formula_structural     Zn2SiO4
_chemical_formula_sum            'O4 Si Zn2'
_chemical_name_mineral           Willemite
_space_group_IT_number           122
_symmetry_space_group_name_Hall  'I -4 2bw'
_symmetry_space_group_name_H-M   'I -4 2 d'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                90
_cell_formula_units_Z            4
_cell_length_a                   7.0069
_cell_length_b                   7.0069
_cell_length_c                   6.4637
_cell_volume                     317.346
_database_code_amcsd             0009399
_exptl_crystal_density_diffrn    4.665
_cod_original_formula_sum        'Zn2 Si O4'
_cod_database_code               9007526
On the crystal chemistry of salt hydrates. VII. The crystal structures of pseudo trisodium orthoarsenate dodecahydrate and the isomorphous phosphate and vanadate salts
Tillmanns, E.; Baur, W. H.; Acta Crystallographica, Section B 27 (1971) 2124–2132; doi:10.1107/S0567740871005454

data_9007527
_publ_section_title
;On the crystal chemistry of salt hydrates. VII. The crystal structures of
 pseudo trisodium orthoarsenate dodecahydrate and the isomorphous phosphate
 and vanadate salts
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              2124
_journal_page_last               2132
_journal_paper_doi               10.1107/S0567740871005454
_journal_volume                  27
_journal_year                    1971
_chemical_formula_structural     Na3PO4(NaOH).167*12H2O
_chemical_formula_sum            'H15.479 Na6.335 O32.335 P2'
_space_group_IT_number           165
_symmetry_space_group_name_Hall  '-P 3 2"c'
_symmetry_space_group_name_H-M   'P -3 c 1'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            2
_cell_length_a                   11.890
_cell_length_b                   11.890
_cell_length_c                   12.671
_cell_volume                     1551.334
_database_code_amcsd             0009400
_exptl_crystal_density_diffrn    1.585
_cod_original_cell_volume        1551.333
_cod_original_formula_sum        'Na6.335 O32.335 P2 H15.479'
_cod_database_code               9007527
_amcsd_formula_title             Na3PO4(NaOH).167*12H2O
On the crystal chemistry of salt hydrates. VII. The crystal structures of pseudo trisodium orthoarsenate dodecahydrate and the isomorphous phosphate and vanadate salts
Tillmanns, E.; Baur, W. H.; Acta Crystallographica, Section B 27 (1971) 2124–2132; doi:10.1107/S0567740871005454

data_9007528
_publ_section_title
;On the crystal chemistry of salt hydrates. VII. The crystal structures of
 pseudo trisodium orthoarsenate dodecahydrate and the isomorphous phosphate
 and vanadate salts
;
_journal_name_full               'Acta Crystallographica, Section B'
_journal_page_first              2124
_journal_page_last               2132
_journal_paper_doi               10.1107/S0567740871005454
_journal_volume                  27
_journal_year                    1971
_chemical_formula_structural     Na3VO4(NaOH).155*12H2O
_chemical_formula_sum            'H15.454 Na6.31 O32.31 V2'
_space_group_IT_number           165
_symmetry_space_group_name_Hall  '-P 3 2"c'
_symmetry_space_group_name_H-M   'P -3 c 1'
_cell_angle_alpha                90
_cell_angle_beta                 90
_cell_angle_gamma                120
_cell_formula_units_Z            2
_cell_length_a                   12.038
_cell_length_b                   12.038
_cell_length_c                   12.833
_cell_volume                     1610.525
_database_code_amcsd             0009401
_exptl_crystal_density_diffrn    1.607
_cod_original_formula_sum        'Na6.31 V2 O32.31 H15.454'
_cod_database_code               9007528
_amcsd_formula_title             Na3VO4(NaOH).155*12H2O