1. R.B. Salama and H.A. El-Obeid, “A Colorimetric Method for the Determination of Isoprenaline Sulphate in Pharmaceutical Preparations.” Analyst, 101, 136-139 (1976).

2. H.A. El-Obeid and M.M.A. Hassan, “PMR Determination of Cineole in Eucalyptusw Oil. Spectroscopy Letters, 12 , 427-38 (1979).
3. H.A. El-Obeid and M.M.A. Hassan, “PMR Assay of Essential Oils: II. Assay of Methylsalicylate in Wintergreen Oil. Spectroscopy Letters, 12 , 555-557 (1979).
4. M.M.A. Hassan, El-Sayed Aboutable and H.A. El-Obeid, “PMR Assay of Essential Oils III. Assay of Allylisothiocyanate in Mustard Oil.” Spectroscopy Letters,13, 199-204(1980).
5. J.S. Mossa, H.A. El-Obeid and M.M.A. Hassan. “PMR Assay of Essential Oils IV. Assay of Carvone in Caraway and Dill Oils.” Spectroscopy Letters,13, 49-57(1980).
H.A. El-Obeid, M.M.A. Hassan and J.S. Mossa, “PMR Assay of Essential Oils V. Assay of Benzyl Benzoate and Benzyl Cinnamate in Balsams.” Spectroscopy Letters, 13, 361-371 (1980).
7. H.A. El-Obeid and A.I. Jado, “A New Colorimetric Assay of Sulfonamides in Pharmaceutical Formulations.” Analytical Lett., 14, 129-136 (1981).
8. H.A. El-Obeid and A.A. Al-Badr, “PMR Assay of Probenecid in Pharmaceutical Formulations.” Pharmazie, 36, 648-9 (1981).
9. Elsayed Aboutable, Humeida A. El-Obeid and M.M.A. Hassan, “PMR Assay of Essential Oils VI. Assay of Oils containing Benzaldehyde, Cinnamaldehyde and Citral”, Pharmazie, 37, 213-214 (1982).
10. Humeida A. El-Obeid, Jaber S. Mossa and Mahmoud M.A. Hassan, “PMR Assay of Essential Oils VII. Assay of Linalool in Coriander Oil”, Analytical Lett., 15(A9), 757-761 (1982).
11 Humeida A. El-Obeid, “Colorimetric Determination of Epinephrine, Norepinephrine and Isoproterenol in Pharmaceutical Dosage Forms”, Analytical Lett., 17(B9), 771-777 (1984).
12 Humeida A. El-Obeid, “Determination of Diethylcarbamazine Citrate in Tablets by Proton Magnetic Resonance”, Spectroscopy Letters, 17, 361-367 (1984).
13. H.A. El-Obeid, A.E. Madani, J.S. Mossa, M.S. Rashed and M.A. Ibrahim, “Spectroscopic Determination of Cinnamaldehyde in Cinnamon and Cassia Oils”, Pharmazie, 39,778-9 (1984).
14. A.M. Wahbi, M.A. Abounassif, H.A. El-Obeid and E.A. Gad-Kareim, “Spectrophotometric Determination of Pirenzepine Dihydrochloride Using A method”. IL Farmaco, 40, 334-338 (1985).
15. A.M. Wahbi, M.A. Abounassif, H.A. El-Obeid and A.M. Al-Julani, “Determination of Pirenzepine Dihydrochloride in the Presence of Degradation Products Using First Derivative Spectrophoto- metry”, Arch. Pharm. Chem., Sci. Ed., 14, 69-72 (1986).
16. A.M. Wahbi, H.A.El-Obeid and E.A.Gad-Karim,”Spectrophotometric Determination of Diethylcarbamazine Citrate via Charge-Transfer Complex”, IL Farmaco, 41, 210-214 (1986).
17. F.S. El-Shafie, E.A. Gad-Kariem, K.A. Al-Rahood, H.A. Al-Khamees and Humeida A. El-Obeid, “Colorimetric Method for the Determination of Ampicillin and Amoxicillin, Analytical Letters, 29(3), 381-393 (1996).
18. H.A. El-Obeid, E.A. Gad-Kariem, K.A. Al-Rashood, H.A. Al-Khamees,
F.S. El-Shafie and G.A.M. Bawazeer, “A Selective Colorimetric Method for the Determination of Penicillins and Cephalosporins with - Aminoacyl Functions”. Analytical Letters, 32, 2809-2823 (1999).
19. E. A. Gagkariem, K. E.E. Ibrahim, N. A. A. Kamil, M. E M. Haga and H.
A. El-Obeid, “A new Spectrophotometric Method for the Determination of Methyldopa”, Saudi Pharmaceutical Journal, 17, 303-309 (2009).
20. E. A. Gadkariem, M. M. Mutasim, K. E. E. Ibrahim and H. A. El-Obeid, “Spectrophotometric methods for the determination of sefprozil in bulk and dosage form”. International J. Biomed. Sci. 5(3): 267-274 (2009).
S. W. Shantier, E. A. Gadkariem, K. E. Ibrahim and H. A. El-Obeid, “Spectrophotometric determination of cefadroxil in pure, bulk and in capsule forms”. E-Journal of Chemistry. http://www.e-journals.net p 1314- 1322 (2011).