## 4 Literature Analysis, Discussion and Future Directions
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**\#** & **Method** & **Category** & **Publication Channel** & **Year** & **Reference** \\ \hline
1 & GAN & Behaviour & Journal (Elsevier) & 2020 & [126] \\
2 & DT & Behaviour & Journal (Elsevier) & 2020 & [127] \\
3 & CRFD & Supervised & Journal (ACM) & 2021 & [128] \\
4 & NN & Supervised & Conference & 2020 & [129] \\
5 & HOTFRED & Supervised & Conference & 2021 & [130] \\
6 & Ramp One-Class SVM & Semi-supervised & Journal (Elsevier) & 2020 & [132] \\
7 & hPSD & Semi-supervised & Journal (IEEE) & 2020 & [133] \\
8 & GPT-2 & Semi-supervised & Journal & 2021 & [134] \\
9 & Self-training & Semi-supervised & Journal (Elsevier) & 2020 & [135] \\
10 & Hadoop & Semi-supervised & Journal (IJARST) & 2020 & [136] \\
11 & CNN & Deep Learning & Conference & 2020 & [137] \\
12 & PV-DBOW & Deep Learning & Journal (Elsevier) & 2020 & [138] \\
13 & LSTM & Deep Learning & Conference & 2020 & [139] \\
14 & LSTM & Deep Learning & Journal (Springer) & 2020 & [140] \\
15 & LSTM + DBN & Deep Learning & Journal (Springer) & 2021 & [141] \\
16 & CNN-BiLSTM & Deep Learning & Journal (Springer) & 2021 & [142] \\
17 & Soft Voting & Linguistics & Journal & 2020 & [143] \\
18 & SRD-LM & Linguistics & Journal (IEEE) & 2020 & [144] \\
19 & PCA & Linguistics & Conference & 2021 & [145] \\
20 & Duplication & Linguistics & Journal (Elsevier) & 2021 & [146] \\
21 & Speech Act Theory & Linguistics & Journal (Elsevier) & 2021 & [147] \\
22 & LIWC & Linguistics & Journal (Elsevier) & 2021 & [148] \\
23 & SVM + DNN & Linguistics & Journal (SAGE) & 2021 & [149] \\
24 & RF, MLP, and K-NN & Ensemble & Journal (Hindawi) & 2020 & [150] \\
25 & ET, RF, Bagging and Boosting & Ensemble & Journal & 2020 & [151] \\
26 & Lightgbm,RF and GBDT & Ensemble & Journal (IEEE) & 2021 & [152] \\
27 & CNN & Ensemble & Journal (Springer) & 2021 & [153] \\
28 & Adaptive Boosting & Ensemble & Journal (Springer) & 2021 & [154] \\
29 & ROSD & Graph-based & Journal & 2020 & [155] \\
30 & DDC & Graph-based & Conference & 2020 & [156] \\
31 & MGSD & Graph-based & Journal (Elsevier) & 2020 & [157] \\
32 & WS & Graph-based & Conference & 2020 & [158] \\
33 & SC-Com & Graph-based & Journal (Elsevier) & 2021 & [159] \\
34 & DT & Sentiment-based & Conference & 2020 & [160] \\
35 & ALOSI & Sentiment-based & Conference & 2021 & [161] \\
36 & GSDNT & Sentiment-based & Journal (Elsevier) & 2021 & [162] \\
37 & RF & Sentiment-based & Journal (Elsevier) & 2021 & [163] \\
38 & NB & Sentiment-based & Conference & 2021 & [164] \\
39 & CBM and BBM & Other approaches & Conference & 2020 & [165] \\
40 & AT & Other approaches & Journal (Elsevier) & 2020 & [166] \\
41 & LDA & Other approaches & Conference & 2020 & [167] \\
42 & SVM, LR and PNN & Other approaches & Journal (Elsevier) & 2021 & [168] \\
43 & REB & Other approaches & Journal (Elsevier) & 2021 & [169] \\
44 & CM & Other approaches & Conference & 2021 & [170] \\
45 & - & Other approaches & Conference & 2021 & [171] \\
46 & EI & Other approaches & Journal (Elsevier) & 2021 & [172] \\
47 & SWOT & Other approaches & Journal (MDPI) & 2021 & [173] \\
48 & (GAN & Other approaches & Journal & 2021 & [174] \\
49 & SVM and k-NN & Other approaches & Conference & 2021 & [175] \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Detailed information of spam reviews detection works.