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- Haensly, Thomas F
- Haer, Oswald, 1809-1883
- Haerdtl, Eduard von, 1861-1897
- Haeredes Ioannis Steinmanni,
- Haerida, Ida
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- Haga, Takuma
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- Hagan, J. H.
- Hagan, John M
- Hagan, N G
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- Hagelberg, W.
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- Hagemann, Dorthe
- Hagen Nursery,
- Hagen, B
- Hagen, B. (Bernhard), 1853-1919
- Hagen, Bianca L.
- Hagen, Brigitte
- Hagen, Christian A
- Hagen, Erin
- Hagen, Heinrich-Otto von, 1933-
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- Hagenbeck, J
- Hagenbuch, Karl W.
- Hagenbuck, Warren W.
- Hagenburger's Specimen Plant Gardens.
- Hagenlund, Linn Katrine
- Hagens, Joseph von 1826-1899
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- Hager, Heather
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- Hager, Joan C.
- Hager, Johannes
- Hagerling, Frederick James, 1876-
- Hagerman, Dwain D
- Hagerstrom Strawberry Nursery,
- Hagerty, Aaron M
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- Haggard Bros.
- Haggard, C. W.
- Haggard, H. Rider (Henry Rider), 1856-1925
- Haggerty, Brian P
- Haggerty, Melvin E. (Melvin Everett), 1875-1937
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- Hagino, Kyoko
- Hagiwara, Masanosuke.
- Hagiwara, Yasuko
- Hagiwara, Yasuo
- Hagle, Susan K.
- Hagler Bailly Consulting, Inc.
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- Haglund, Gustaf
- Haglund, Karl
- Haglund, Laila 1934-
- Hagmann, Gottfried
- Hagmann, Lyle Everest, 1915-
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- Hagos, Tewolde
- Hágsater, Eric
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- Hague, Florence S
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- Hahn, Donald E.
- Hahn, Eduard, 1856-1928
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- Hahn, Glenn G.
- Hahn, Hans Jurgen
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- Hahn, Jamul,
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- Hahn, Norma Segatti, 1955-
- Hahn, Otto
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- Hahn, Steffen
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- Hahn, William James
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- Hahn's Iris Garden.
- Hahn'sche Hofbuchhandlung,
- Hahn-Weinheimer, P
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- Hai Yan, Wang
- Hai, Do Van
- Hai, Dong Jin
- Hai, Tran Van
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- Haidar, Ricardo Flores, 1980-
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- Haig, John G
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- Haigh, Simone
- Haight, Bruce M.
- Haight, E. M.
- Haight, Frank Joshua, 1893-
- Haight, R. J. (Rufus J.)
- Haight, Robert G., 1955-
- Haigwood, Jim
- Haij, Bernhard Julius
- Haij, Isaacus,
- Hail, Anthony Godwin, 1924-
- Haila, Yrjö
- Haile, James
- Haile, Kelly C
- Haile, Mitiku
- Haile, N. S. (Neville Seymour)
- Haile, Zeweldi
- Haile-Dean Seed Co.
- Haile-Selassie, Yohannes
- Haileybury Natural Science Society.
- Hailman, Jack P
- Hails, John R.
- Hails, Rosemary
- Hailstone, T S
- Haime, Jules, 1824-1856
- Haimovici, Manuel
- Hain, James H. W.
- Hain, Melchior Gottfried, 1659-1719
- Hainault, Robert
- Haine, Brendan
- Haines City Nurseries.