On Overleaf, I am using this type of bio:
\begin{thebibliography}{}
\bibitem{GI}
Belinskii, A, & Klyshko, D. Two-photon optics: diffraction, holography, and transformation of two-dimensional signals. Sov. Phys. JETP 78, 259 (1994).
\bibitem{Pittman}
Pittman, T. B., Shih, Y. H., Strekalov, D. V. & Sergienko, A. V. Optical imaging by means of two-photon quantum entanglement. Phys. Rev. A 52, R34232 (1995).
\bibitem{Thermal}
Gatti, A., Brambilla, E., Bache, M. & Lugiato, L. A. Ghost Imaging with Thermal Light: Comparing Entanglement and Classical Correlation. Phys. Rev. Lett. 93,
093602 (2004).
\end{thebibliography}
When I cite \cite{GI, Pittman, Thermal} I'd like [1-3] but I get [1,2,3]. How can I change it?
\usepackage{cite}or with\usepackage[numbers, sort&compress]{natbib}. (Do not load both packages at the same time!) Since your manualthebibliographydoes not use the optional argument of\bibitemto pass on author and year data, it probably makes little sense to usenatbib, so in your setting I'd go for\usepackage{cite}.&s to\&s to avoid errors.Belinskii, A,should probably beBelinskii, A.,