Letax record \documentclass{}, authoryear attribute is used

This article takes elsevier Journal template for For example , Download link CTAN: /tex-archive/macros/latex/contrib/elsarticle：
How to use reference ：https://blog.csdn.net/weixin_43955917/article/details/95880651

The above three methods correspond to .tex The documents are ：
elsarticle-template-num-names.tex author + Numbers   
elsarticle-template-harv.tex author + year
elsarticle-template-num.tex Number only

One 、 Reference format ( according to Author-Year Format )

\bibitem[Authors(Year)]{label} .....

example ：\bibitem[Hu et al.(2020)]{Hu2020} Hu, Sixing and Lee, Gim Hee. Image-based geo-localization using satellite imagery. IJCV, 2020, 128(5): 1205-1219. 

Citation format ：

\citet{<label>} ==> Jones et al. [21]
\citep{<label>} ==> [21]

1. Show author plus number ------ elsarticle-template-num-names.tex author + Numbers   

 Statement ：\documentclass[final,3p,times,twocolumn]{elsarticle}

 reference   How to quote 
\citet{Hu2020} ===> Hu et al. [1] 
\citep[{Hu2020} ===> [1]

2. Show author plus year ------- elsarticle-template-harv.tex author + year

 Statement ：\documentclass[final,3p,times,twocolumn,authoryear]{elsarticle}

\citet{Hu2020} ===> Hu et al. (2020)
\citep[{Hu2020} ===> (Hu et al., 2020)

Two 、 Reference format ( Normal format , Only numbers )

\bibitem{label} .....

example ：\bibitem{Hu2020} Hu, Sixing and Lee, Gim Hee. Image-based geo-localization using satellite imagery. IJCV, 2020, 128(5): 1205-1219. 

Citation format ：

\citet{<label>} ==>  (author?) [21] # There will be exceptions 
\citep{<label>} ==> [21]

1. Show numbers only ------ elsarticle-template-num.tex Number only

\citet{Hu2020} ===> (author?) [1]
\citep[{Hu2020} ===> [1]